Multi-frequency reduction of fluid droplet

ABSTRACT

A signal generator has a generator output. The signal generator is configured to generate first and second signals at the generator output. The first signal has a first frequency, and the second signal has a second frequency. Switching circuitry has a circuitry input and a circuitry output. The circuitry input is coupled to the generator output. The circuitry output is adapted to be coupled to an ultrasonic transducer mechanically coupled with a surface. The switching circuitry is configured to: provide the first signal to the ultrasonic transducer at the first frequency to reduce a fluid droplet on the surface from a first size to a second size; and provide the second signal to the ultrasonic transducer at the second frequency to reduce the fluid droplet from the second size to a third size.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/492,286 filed Apr. 20, 2017, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/407,762 filed Oct. 13, 2016and U.S. Provisional Patent Application Ser. No. 62/400,171 filed Sep.27, 2016, the entireties of which are incorporated herein by reference.

BACKGROUND

This relates generally to ultrasonics, and more particularly tomulti-frequency reduction of a fluid droplet.

Unfortunately, the number of motor vehicle deaths appears to beincreasing every year. This trend is caused by a variety of reasons,including an increase in the driving population. But more engineeringeffort is needed to reduce risk of death or serious injury inautomobiles. In addition to avoiding risks to drivers and passengers,more robust obstacle and collision avoidance systems are required toreduce the high cost of damage to automobiles and other property due tocollisions.

Fortunately, new technologies are becoming available that manufacturerscan incorporate into new automobiles at a reasonable cost. Somepromising technologies that may help to improve obstacle and collisionavoidance systems are digital camera based surround view and cameramonitoring systems. In some cases, cameras can increase safety by beingmounted in locations that can give drivers access to alternativeperspectives, which is otherwise diminished or unavailable to thedriver's usual view through windows or mirrors. While mounting one ormore cameras for alternative views can provide many advantages, somechallenges may remain.

SUMMARY

A signal generator has a generator output. The signal generator isconfigured to generate first and second signals at the generator output.The first signal has a first frequency, and the second signal has asecond frequency. Switching circuitry has a circuitry input and acircuitry output. The circuitry input is coupled to the generatoroutput. The circuitry output is adapted to be coupled to an ultrasonictransducer mechanically coupled with a surface. The switching circuitryis configured to: provide the first signal to the ultrasonic transducerat the first frequency to reduce a fluid droplet on the surface from afirst size to a second size; and provide the second signal to theultrasonic transducer at the second frequency to reduce the fluiddroplet from the second size to a third size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is partial block diagram of a system according to an embodimentincluding an apparatus that can expel fluid from a droplet on an opticalsurface using an ultrasonic transducer mechanically coupled to theoptical surface.

FIG. 2 is a more detailed diagram of the system shown in FIG. 1according to an embodiment.

FIG. 3A is a diagram of impedance versus frequency for an exampleultrasonic transducer mechanically coupled to an example optical surfaceaccording to an embodiment.

FIG. 3B is a diagram of example droplet size reduction versus frequencyaccording to an embodiment.

FIGS. 4A-4F show a flowchart representative of example machine readableinstructions that may be executed to implement the example system toexpel fluid from the droplet on the optical surface using the ultrasonictransducer mechanically coupled to the optical surface, according to anembodiment as shown in the example of FIG. 1.

FIG. 5 is a block diagram of an example processing platform capable ofexecuting the machine readable instructions of FIGS. 4A-4F to implementthe example system to expel fluid from the droplet on the opticalsurface using the ultrasonic transducer mechanically coupled to theoptical surface, according to an embodiment as shown in the example ofFIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

U.S. Pat. No. 10,384,239 is incorporated by reference in its entirety.

FIG. 1 is partial block diagram of a system 100 that can expel fluidfrom a droplet 102 on an optical surface 104 using an ultrasonictransducer 106 mechanically coupled to the optical surface 104. Forexample, the ultrasonic transducer 106 can be a piezoelectric ultrasonictransducer 106 including a piezoelectric material (e.g., lead zirconatetitanate PZT or niobium doped lead zirconate titanate PNZT.) Themechanical coupling of the ultrasonic transducer 106 with the opticalsurface 104 is representatively illustrated in the drawings by a dashedline box that encompasses the ultrasonic transducer 106 mechanicallycoupled to the optical surface 104. The fluid droplet 102 can bedisposed on the optical surface 104 and can be coupled with theultrasonic transducer 106 through the optical surface 104. Accordingly,such coupling of the fluid droplet 102, the ultrasonic transducer 106and the optical surface 104 is representatively illustrated in thedrawings by the dashed line box that encompasses the fluid droplet 102,the ultrasonic transducer 106 and the optical surface 104. In theexample of FIG. 1, the ultrasonic transducer 106 mechanically coupled tothe optical surface 104 and has a plurality of resonant frequency bands(e.g., first and second resonant frequency bands).

The example of FIG. 1 shows a first amplifier 108 a having a firstoutput impedance 110 a. A first filter 112 a (e.g., first filter network112 a) is tuned (e.g., by its corresponding filter component values)within the first resonant frequency band to facilitate matching thefirst output impedance 110 a of the first amplifier 108 a with impedanceof the ultrasonic transducer 106 mechanically coupled to the opticalsurface 104 and to reduce by atomization the fluid droplet 102 from afirst droplet size 102 a to a second droplet size 102 b. A second filter114 a (e.g., second filter network 114 a) is tuned (e.g., by itscorresponding filter component values) within the second resonantfrequency band to facilitate matching the first output impedance 110 aof the first amplifier 108 a with impedance of the ultrasonic transducer106 mechanically coupled to the optical surface 104 and to reduce byatomization the fluid droplet 102 from the second droplet size 102 b toa third droplet size 102 c. In the drawings: the first droplet size 102a is representatively illustrated using a dash-dot-dot-dash line style;the second droplet size 102 b is representatively illustrated using adash-dot-dash line style; and the third droplet size 102 c isrepresentatively illustrated using solid line style.

In the example of FIG. 1, the first filter 112 a (e.g., first filternetwork 112 a) can be tuned (e.g., by its corresponding filter componentvalues) higher in frequency than the second filter 114 a (e.g., secondfilter network 114 a.) Similarly, the first resonant frequency band ofthe ultrasonic transducer 106 mechanically coupled to the opticalsurface 104 can be higher in frequency than the second resonantfrequency band of the ultrasonic transducer 106 mechanically coupled tothe optical surface 104. In the example of FIG. 1, the first resonantfrequency band to reduce the fluid droplet 102 from the first dropletsize 102 a to the second droplet size 102 b is higher in frequency thanthe second resonant frequency band to reduce the fluid droplet 102 fromthe second droplet size 102 b to the third droplet size. For example,the first filter 112 a (e.g., first filter network 112 a) can be tuned(e.g., by its corresponding filter component values) within the firstresonant frequency band of the ultrasonic transducer 106 mechanicallycoupled to the optical surface 104 to reduce by atomization the fluiddroplet 102 from the first droplet size 102 a to the second droplet size102 b, and so as to be higher in frequency than the second filter 114 a(e.g., second filter network 114 a) tuned (e.g., by its correspondingfilter component values) within the second resonant frequency band ofthe ultrasonic transducer 106 mechanically coupled to the opticalsurface 104 to reduce by atomization the fluid droplet 102 from thesecond droplet size 102 b to the third droplet size 102 c.

In the example of FIG. 1, a circuitry controller 116 can be coupled withan input 118 a, 120 a of the first amplifier 108 a to generate a firstsignal at an input 122 a of ultrasonic transducer 106. The first signalat the input 122 a of the ultrasonic transducer 106 includes a firstfrequency within the first resonant frequency band of the ultrasonictransducer 106 mechanically coupled to the optical surface 104. In someexamples, the first frequency of the first signal can be a first sweepof frequencies (e.g., a first frequency sweep) within the first resonantfrequency band of the ultrasonic transducer 106 mechanically coupled tothe optical surface 104. Filter activation (and deactivation), as wellas activation (and deactivation) of the ultrasonic transducer 106, canbe carried out by filter switching circuitry 124, which is depicted inthe drawings using stippled lines. For example, the filter switchingcircuitry 124 can be coupled between the circuitry controller 116 andthe first filter 112 a (e.g., first filter network 112 a) to activatethe first filter 112 a (e.g. first filter network 112 a) in response toa first control activation signal received from the circuitry controller116 at an input 126 of the filter switching circuitry 124. For example,the filter switching circuitry 124 can include a first filter switchcontroller 128 having a first low side switch control output 128 a and afirst high side switch control output 128 b. The first low side switchcontrol output 128 a of the first switch controller 128 can be coupledwith a first low side switch 130 a to control operation of the first lowside switch 130 a, for example, operation between a conducting or closedstate of the first low side switch 130 a and a non-conducting or openstate of the first low side switch 130 a. The first high side switchcontrol output 128 b can be coupled with a first high side switch 130 bto control operation of the first high side switch 130 b, for example,operation between a conducting or closed state of the first high sideswitch 130 b and a non-conducting or open state of the first high switch130 b. As shown in the example of FIG. 1, the first low side switch 130a can be coupled between a ground reference and the first filter 112 a(e.g., first filter network 112 a.) As shown in the example of FIG. 1,the first high side switch 130 b can be coupled between the first filter112 a (e.g., first filter network 112 a) and input 122 a of theultrasonic transducer 106.

For example, first switch controller 128 can control both first low andhigh side switches 130 a, 130 b to be in a closed or conducting state,so as to activate the first filter 112 a (e.g. first filter network 112a) in response to the first control activation signal received from thecircuitry controller 116 at the input 126 of the filter switchingcircuitry 124. For example, first switch controller 128 can control bothfirst low and high side switches 130 a, 130 b to be in the open ornon-conducting state, so as to deactivate the first filter 112 a (e.g.first filter network 112 a) in response to a first control deactivationsignal received from the circuitry controller 116 at the input 126 ofthe filter switching circuitry 124.

In the example of FIG. 1, the circuitry controller 116 can also becoupled with the input 118 a, 120 a of the first amplifier 108 a togenerate a second signal at the input 122 a of ultrasonic transducer106. The second signal at the input 122 a of the ultrasonic transducer106 includes a second frequency within the second resonant frequencyband of the ultrasonic transducer 106 mechanically coupled to theoptical surface 104. In some examples, the second frequency of thesecond signal can be a second sweep of frequencies (e.g., a secondfrequency sweep) within the second resonant frequency band of theultrasonic transducer 106 mechanically coupled to the optical surface104. In the example of FIG. 1, the filter switching circuitry 124 can becoupled between the circuitry controller 116 and the second filter 114 a(e.g., second filter network 114 a) to activate the second filter 114 a(e.g. second filter network 114 a) in response to a second controlactivation signal received from the circuitry controller 116 at theinput 126 of the filter switching circuitry 124. For example, the filterswitching circuitry 124 can include a second filter switch controller138 having a second low side switch control output 138 a and a secondhigh side switch control output 138 b. The second low side switchcontrol output 138 a of the second switch controller 138 can be coupledwith a second low side switch 140 a to control operation of the secondlow side switch 140 a, for example, operation between a conducting orclosed state of the second low side switch 140 a and a non-conducting oropen state of the second low side switch 140 a. The second high sideswitch control output 138 b can be coupled with a second high sideswitch 140 b to control operation of the second high side switch 140 b,for example, operation between a conducting or closed state of thesecond high side switch 140 b and a non-conducting or open state of thesecond high switch 140 b. As shown in the example of FIG. 1, the secondlow side switch 140 a can be coupled between a ground reference and thesecond filter 114 a (e.g., second filter network 114 a.) As shown in theexample of FIG. 1, the second high side switch 140 b can be coupledbetween the second filter 114 a (e.g., second filter network 114 a) andinput 122 a of the ultrasonic transducer 106.

For example, second switch controller 138 can control both second lowand high side switches 140 a, 140 b to be in a closed or conductingstate, so as to activate the second filter 114 a (e.g. second filternetwork 114 a) in response to the second control activation signalreceived from the circuitry controller 116 at the input 126 of thefilter switching circuitry 124. For example, second switch controller138 can control both second low and high side switches 140 a, 140 b tobe in the open or non-conducting state, so as to deactivate the secondfilter 114 a (e.g. second filter network 114 a) in response to a secondcontrol deactivation signal received from the circuitry controller 116at the input 126 of the filter switching circuitry 124.

Also included in the example of FIG. 1 is a second amplifier 108 bhaving a second amplifier output impedance 110 b. The first additionalfilter 112 b (e.g., first additional filter network 112 b) is tuned(e.g., by its corresponding filter component values) within the firstresonant frequency band to facilitate matching the second outputimpedance 110 b of the second amplifier 108 b with impedance of theultrasonic transducer 106 mechanically coupled to the optical surface104 and to reduce by atomization the fluid droplet 102 from a firstdroplet size 102 a to a second droplet size 102 b. The second additionalfilter 114 b (e.g., second additional filter network 114 b) is tuned(e.g., by its corresponding filter component values) within the secondresonant frequency band to facilitate matching the second outputimpedance 110 b of the second amplifier 108 b with impedance of theultrasonic transducer 106 mechanically coupled to the optical surface104 and to reduce by atomization the fluid droplet 102 from the seconddroplet size 102 b to the third droplet size 102 c.

Also included in the example of FIG. 1 are a pair of ultrasonictransducer couplers 142 a, 142 b (e.g., connectors 142 a, 142 b). Forexample, electrodes of ultrasonic transducer 106 can be soldered towires, which can be attached to a circuit board via connectors 142 a,142 b. The pair of ultrasonic transducer couplers 142 a, 142 b cancouple a bridge tied load including the ultrasonic transducer 106between the first amplifier 108 a and the second amplifier 108 b. Forexample, the pair of ultrasonic transducer couplers 142 a, 142 b cancouple the ultrasonic transducer 106 between the first amplifier 108 aand the second amplifier 108 b as the bridge tied load 108 b. Inaddition to the first filter 112 a (e.g. first filter network 112 a),the example of FIG. 1 includes a first additional filter 112 b (e.g.first additional filter network 112 b.) The pair of ultrasonictransducer couplers 142 a, 142 b can couple the bridge tied loadincluding the ultrasonic transducer 106 between the first filter 112 a(e.g., first filter network 112 a) and the first additional filter 112 b(e.g., first additional filter network 112 b.) For example, the pair ofultrasonic transducer couplers 142 a, 142 b can couple the ultrasonictransducer 106 between the first filter 112 a (e.g., first filternetwork 112 a) and the first additional filter 112 b (e.g., firstadditional filter network 112 b) as the bridge tied load 106.

The first filter 112 a (e.g., first filter network 112 a) and the firstadditional filter 112 b (e.g., first additional filter network 112 b)can be included in a first balanced filter 112 a, 112 b. The pair ofultrasonic transducer couplers 142 a, 142 b can be coupled between thefirst filter 112 a (e.g., first filter network 112 a) and the firstadditional filter 112 b (e.g., first additional filter network 112 b) inthe first balanced filter 112 a, 112 b including the first filter 112 a(e.g., first filter network 112 a) and the first additional filter 112 b(e.g., first additional filter network 112 b.)

The first balanced filter 112 a, 112 b may be desired for its qualityfactor relative to quality factor of the first filter (e.g. first filternetwork 112 a) alone. For example, the first filter network 112 a canhave a first filter network quality factor. The first balanced filter112 a, 112 b including the first filter network 112 a and the firstadditional filter network 112 b can have a first balanced filter qualityfactor. The first balanced filter quality factor of the first balancedfilter 112 a, 112 b can be greater than the first filter network qualityfactor of the first filter network 112 a.

The first filter 112 a can be matched pair tuned with the firstadditional filter 112 b within the first resonant frequency band tofacilitate matching the first output impedance 110 a of the firstamplifier 108 a with impedance of the ultrasonic transducer 106mechanically coupled to the optical surface 104 and to reduce byatomization the fluid droplet 102 from the first droplet size 102 a tothe second droplet size 102 b.

Similarly, in addition to the second filter 114 a (e.g. second filternetwork 114 a), the example of FIG. 1 includes a second additionalfilter 114 b (e.g. second additional filter network 112 b.) The pair ofultrasonic transducer couplers 142 a, 142 b can couple the bridge tiedload including the ultrasonic transducer 106 between the second filter114 a (e.g., second filter network 114 a) and the second additionalfilter 114 b (e.g., second additional filter network 114 b.) Forexample, the pair of ultrasonic transducer couplers 142 a, 142 b cancouple the ultrasonic transducer 106 between the second filter 114 a(e.g., second filter network 114 a) and the second additional filter 114b (e.g., second additional filter network 114 b) as the bridge tied load106.

The second filter 114 a (e.g., second filter network 114 a) and thesecond additional filter 114 b (e.g., second additional filter network114 b) can be included in a second balanced filter 114 a, 114 b. Thepair of ultrasonic transducer couplers 142 a, 142 b can be coupledbetween the second filter 114 a (e.g., second filter network 114 a) andthe second additional filter 114 b (e.g., second additional filternetwork 114 b) in the second balanced filter 114 a, 114 b including thesecond filter 114 a, (e.g., second filter network 114 a) and the secondadditional filter 114 b (e.g., second additional filter network 114 b.)

Similar to what was discussed with respect to the first balanced filter112 a, 112 b, the second balanced filter 114 a, 114 b may be desired forits quality factor relative to quality factor of the second filter (e.g.second filter network 114 a) alone. For example, the second filternetwork 114 a can have a second filter network quality factor. Thesecond balanced filter 114 a, 114 b including the second filter network114 a and the second additional filter network 114 b can have a secondbalanced filter quality factor. The second balanced filter qualityfactor of the second balanced filter 114 a, 114 b can be greater thanthe second filter network quality factor of the second filter network114 a.

The second filter 114 a can be matched pair tuned with the secondadditional filter 114 b within the second resonant frequency band tofacilitate matching the first output impedance 110 a of the firstamplifier 108 a with impedance of the ultrasonic transducer 106mechanically coupled to the surface 104 and to reduce by atomization thefluid droplet from the second droplet size 102 b to the third dropletsize 102 c.

In the example of FIG. 1, the circuitry controller 116 can be coupledwith an additional input 118 b, 120 b of the second amplifier 108 b togenerate a first additional signal at an additional input 122 b ofultrasonic transducer 106. The first additional signal at the additionalinput 122 b of the ultrasonic transducer 106 includes the firstfrequency within the first resonant frequency band of the ultrasonictransducer 106 mechanically coupled to the optical surface 104. Forexample, the filter switching circuitry 124 can be coupled between thecircuitry controller 116 and the first additional filter 112 b (e.g.,first additional filter network 112 b) to activate the first additionalfilter 112 b (e.g. first additional filter network 112 b) in response tothe first control activation signal received from the circuitrycontroller 116 at the input 126 of the filter switching circuitry 124.For example, the first filter switch controller 128 of the filterswitching circuitry 124 can include having a first additional low sideswitch control output 128 c and a first additional high side switchcontrol output 128 d. The first additional low side switch controloutput 128 c of the first switch controller 128 can be coupled with afirst additional low side switch 150 a to control operation of the firstadditional low side switch 150 a, for example, operation between aconducting or closed state of the first additional low side switch 150 aand a non-conducting or open state of the first additional low sideswitch 150 a. The first additional high side switch control output 128 dcan be coupled with a first additional high side switch 150 b to controloperation of the first additional high side switch 150 b, for example,operation between a conducting or closed state of the first additionalhigh side switch 150 b and a non-conducting or open state of the firstadditional high switch 150 b. As shown in the example of FIG. 1, thefirst additional low side switch 150 a can be coupled between the groundreference and the first additional filter 112 b (e.g., first additionalfilter network 112 b.) As shown in the example of FIG. 1, the firstadditional high side switch 150 b can be coupled between the firstadditional filter 112 b (e.g., first additional filter network 112 b)and additional input 122 b of the ultrasonic transducer 106.

For example, first switch controller 128 can control both the firstadditional low side switch 150 a and the first additional high sideswitch 150 b to be in a closed or conducting state, so as to activatethe first additional filter 112 b (e.g. first additional filter network112 b) in response to the first control activation signal received fromthe circuitry controller 116 at the input 126 of the filter switchingcircuitry 124. At the same time, the first switch controller 128 canalso control both first low and high side switches 130 a, 130 b to be inthe closed or conducting state, so as to activate the first filter 112 a(e.g. first filter network 112 a) in response to the first controlactivation signal received from the circuitry controller 116 at theinput 126 of the filter switching circuitry 124. Accordingly, inresponse to the first control activation signal received from thecircuitry controller 116 at the input 126 of the filter switchingcircuitry 124, the first switch controller 128 can activate both thefirst filter 112 a (e.g. first filter network 112 a) and the firstadditional filter 112 b (e.g. first additional filter network 112 b.)Moreover, since the first balanced filter 112 a, 112 b can include boththe first filter 112 a (e.g., first filter network 112 a) and the firstadditional filter network 112 b (e.g. first additional filter network112 b), in response to the first control activation signal received fromthe circuitry controller 116 at the input 126 of the filter switchingcircuitry 124, the first switch controller 128 can activate the firstbalanced filter 112 a, 112 b.

For example, first switch controller 128 can control both the firstadditional low side switch 150 a and the first additional high sideswitch 150 b to be in an open or non-conducting state, so as todeactivate the first additional filter 112 b (e.g. first additionalfilter network 112 b) in response to the first control deactivationsignal received from the circuitry controller 116 at the input 126 ofthe filter switching circuitry 124. At the same time, the first switchcontroller 128 can also control both first low and high side switches130 a, 130 b to be in the open or non-conducting state, so as todeactivate the first filter 112 a (e.g. first filter network 112 a) inresponse to the first control deactivation signal received from thecircuitry controller 116 at the input 126 of the filter switchingcircuitry 124. Accordingly, in response to the first controldeactivation signal received from the circuitry controller 116 at theinput 126 of the filter switching circuitry 124, the first switchcontroller 128 can deactivate both the first filter 112 a (e.g. firstfilter network 112 a) and the first additional filter 112 b (e.g. firstadditional filter network 112 b.) Moreover, since the first balancedfilter 112 a, 112 b can include both the first filter 112 a (e.g., firstfilter network 112 a) and the first additional filter network 112 b(e.g. first additional filter network 112 b), in response to the firstcontrol deactivation signal received from the circuitry controller 116at the input 126 of the filter switching circuitry 124, the first switchcontroller 128 can deactivate the first balanced filter 112 a, 112 b.

In the example of FIG. 1, the circuitry controller 116 can also becoupled with the additional input 118 b, 120 b of the second amplifier108 b to generate a second additional signal at the additional input 122b of ultrasonic transducer 106. The second additional signal at theadditional input 122 b of the ultrasonic transducer 106 includes thesecond frequency within the second resonant frequency band of theultrasonic transducer 106 mechanically coupled to the optical surface104. For example, the filter switching circuitry 124 can be coupledbetween the circuitry controller 116 and the second additional filter114 b (e.g., second additional filter network 114 b) to activate thesecond additional filter 114 b (e.g. second additional filter network114 b) in response to the second control activation signal received fromthe circuitry controller 116 at the input 126 of the filter switchingcircuitry 124. For example, the second filter switch controller 138 ofthe filter switching circuitry 124 can include a second additional lowside switch control output 138 c and a second additional high sideswitch control output 138 d. The second additional low side switchcontrol output 138 c of the second switch controller 138 can be coupledwith a second additional low side switch 160 a to control operation ofthe second additional low side switch 160 a, for example, operationbetween a conducting or closed state of the second additional low sideswitch 160 a and a non-conducting or open state of the second additionallow side switch 160 a. The second high side switch control output 138 dcan be coupled with a second additional high side switch 160 b tocontrol operation of the second additional high side switch 160 b, forexample, operation between a conducting or closed state of the secondadditional high side switch 160 b and a non-conducting or open state ofthe second additional high switch 160 b.

As shown in the example of FIG. 1, the second additional low side switch160 a can be coupled between the ground reference and the secondadditional filter 114 b (e.g., second additional filter network 114 b.)As shown in the example of FIG. 1, the second additional high sideswitch 160 b can be coupled between the second additional filter 114 b(e.g., second additional filter network 114 b) and additional input 122b of the ultrasonic transducer 106. For example, second switchcontroller 138 can control both the second additional low side switch160 a and the second additional high side switch 160 b to be in a closedor conducting state, so as to activate the second additional filter 114b (e.g. second additional filter network 114 b) in response to thesecond control activation signal received from the circuitry controller116 at the input 126 of the filter switching circuitry 124. At the sametime, the second switch controller 138 can also control both second lowand high side switches 140 a, 140 b to be in the closed or conductingstate, so as to activate the second filter 114 a (e.g. second filternetwork 112 b) in response to the second control activation signalreceived from the circuitry controller 116 at the input 126 of thefilter switching circuitry 124. Accordingly, in response to the secondcontrol activation signal received from the circuitry controller 116 atthe input 126 of the filter switching circuitry 124, the second switchcontroller 138 can activate both the second filter 114 a (e.g. secondfilter network 114 a) and the second additional filter 114 b (e.g.second additional filter network 114 b.) Moreover, since the secondbalanced filter 114 a, 114 b can include both the second filter 114 a(e.g., second filter network 112 a) and the second additional filternetwork 114 b (e.g. second additional filter network 114 b), in responseto the second control activation signal received from the circuitrycontroller 116 at the input 126 of the filter switching circuitry 124,the second switch controller 138 can activate the second balanced filter114 a, 114 b.

For example, second switch controller 138 can control both the secondadditional low side switch 160 a and the second additional high sideswitch 160 b to be in an open or non-conducting state, so as todeactivate the second additional filter 114 b (e.g. second additionalfilter network 114 b) in response to the second control deactivationsignal received from the circuitry controller 116 at the input 126 ofthe filter switching circuitry 124. At the same time, the second switchcontroller 138 can also control both second low and high side switches140 a, 140 b to be in the open or non-conducting state, so as todeactivate the second filter 114 a (e.g. second filter network 114 b) inresponse to the second control deactivation signal received from thecircuitry controller 116 at the input 126 of the filter switchingcircuitry 124. Accordingly, in response to the second controldeactivation signal received from the circuitry controller 116 at theinput 126 of the filter switching circuitry 124, the second switchcontroller 138 can deactivate both the second filter 114 a (e.g. secondfilter network 114 a) and the second additional filter 114 b (e.g.second additional filter network 114 b.) Moreover, since the secondbalanced filter 114 a, 114 b can include both the second filter 114 a(e.g., second filter network 114 a) and the second additional filternetwork 114 b (e.g. second additional filter network 114 b), in responseto the second control deactivation signal received from the circuitrycontroller 116 at the input 126 of the filter switching circuitry 124,the second switch controller 138 can deactivate the second balancedfilter 114 a, 114 b.

As shown in the example of FIG. 1, the optical surface 104 can beoriented within a gravitational field so that a component of thegravitational field that is tangential to the surface 104 (e.g., asdepicted for by downward arrow tangential to surface 104) operates uponthe fluid droplet 102. This orientation can be achieved, for example,while activating the ultrasonic transducer 106 that is mechanicallycoupled to the optical surface 104 to expel fluid of the fluid droplet102 from the optical surface. For example, the foregoing orienting ofthe optical surface 104 can be orienting the optical surface 104 withinthe gravitational field so that the component of the gravitational fieldthat is tangential to the optical surface 104 is greater than acomponent of the gravitation field that is normal into the opticalsurface 104.

As mentioned previously, in the example of FIG. 1 filter activation (anddeactivation), as well as activation (and deactivation) of theultrasonic transducer 106, can be carried out by filter switchingcircuitry 124, which is depicted in the drawings using stippled lines.For example, the filter switching circuitry 124 can be coupled betweenthe circuitry controller 116 and the first filter 112 a (e.g., firstfilter network 112 a) to activate the first filter 112 a (e.g. firstfilter network 112 a) in response to a first control activation signalreceived from the circuitry controller 116 at an input 126 of the filterswitching circuitry 124. Similarly, at the same time, the filterswitching circuitry 124 can be coupled between the circuitry controller116 and the first additional filter 112 b (e.g., first additional filternetwork 112 b) to activate the first additional filter 112 b (e.g. firstadditional filter network 112 b) in response to the first controlactivation signal received from the circuitry controller 116 at theinput 126 of the filter switching circuitry 124.

As shown in the example of FIG. 1, the circuitry controller 116 can becoupled with the input 118 a, 120 a of the first amplifier 108 a togenerate the first signal at the input 122 a of ultrasonic transducer106. Similarly, at the same time, the circuitry controller 116 can becoupled with the additional input 118 b, 120 b of the second amplifier108 b to generate the first additional signal at the additional input122 b of ultrasonic transducer 106. The first signal at the input 122 aof the ultrasonic transducer 106 includes the first frequency within thefirst resonant frequency band of the ultrasonic transducer 106mechanically coupled to the optical surface 104. Similarly, as alreadydiscussed, the first additional signal at the additional input 122 b ofthe ultrasonic transducer 106 likewise can include the first frequencywithin the first resonant frequency band of the ultrasonic transducer106 mechanically coupled to the optical surface 104. The first signaland the first additional signal can be antiphase (e.g.,one-hundred-and-eighty degrees out of phase) with one another.

The circuitry controller 116 can begin ramping up the amplitude of thefirst signal at the ultrasonic transducer 106 from a predeterminedinitial amplitude level of the first signal to a predetermined fullamplitude level of the first signal. At the same time, in a similarlyway, circuitry controller 116 can also begin ramping up the amplitude ofthe first additional signal at the ultrasonic transducer 106 from apredetermined initial amplitude level of the first additional signal toa predetermined full amplitude level of the first additional signal.

For example, respective amplitudes of the first signal and the firstadditional signal can be ramped up (e.g., increased) by the circuitrycontroller 116 from their respective predetermined initial amplitudelevels to their respective predetermined full amplitude levels at apredetermined ramp up rate. For example, the circuitry controller 116can begin ramping up (e.g., increasing) respective amplitudes of thefirst signal and the first additional signal at the predetermined rampup rate. The circuitry controller 116 can continue ramping up respectiveamplitudes of the first signal and the first additional signal at thepredetermined ramp up rate, by increasing respective amplitudes of thefirst signal and first additional signal, while respective predeterminedfull amplitude levels of the first signal and the first additionalsignal have not yet been reached. Because the circuitry controller 116can control and/or increase and/or set the respective amplitudes of thefirst signal and first additional signal, the circuitry controller 116can determine that ramping up of the first signal and the firstadditional signal is finished. For example, as the circuitry controller116 is finishing ramping up, the circuitry controller 116 can controland/or increase and/or set the respective amplitudes of the first signaland first additional signal to their respective predetermined fullamplitude levels. For example, after the circuitry controller 116controls and/or increases and/or sets the respective amplitudes of thefirst signal and first additional signal to their respectivepredetermined full amplitude levels, the circuitry controller 116 candetermine that ramping up (e.g. increasing amplitude of the first signaland first additional signal) is finished.

In another example of ramping up, an amplitude sensor 162 can include ananalog differential amplifier that can differentially sense voltageacross the input 122 a and the additional input 122 b of the ultrasonictransducer 106. The voltage differentially sensed by the analogdifferential amplifier across the input 122 a and the additional input122 b of the ultrasonic transducer 106 is indicative of respectiveamplitudes of the first signal and the first additional signal inantiphase with one another. The first signal and the first additionalsignal can be ramped up by the circuitry controller 116 from theirrespective predetermined initial amplitude levels to their respectivepredetermined full amplitude levels at a predetermined ramp up rate. Forexample, the circuitry controller 116 can begin ramping up the firstsignal and the first additional signal at the predetermined ramp uprate. The circuitry controller 116 can continue ramping up the firstsignal and the first additional signal at the predetermined ramp uprate, by increasing respective amplitudes of the first signal and firstadditional signal, while respective predetermined full amplitude levelsof the first signal and the first additional signal have not yet beenreached. For example, as the circuitry controller 116 is finishingramping up, the circuitry controller 116 can use the analog differentialamplifier in differentially sensing the voltage across the input 122 aand the additional input 122 b of the ultrasonic transducer. Thismeasurement can be the first sensed amplitude 164 a and can beindicative of respective amplitudes of the first signal and the firstadditional signal in antiphase with one another. In this example, theamplitude comparator 166 can compare the first sensed amplitude 164 a tothe ascending target amplitude 168 a, for example, to determine whetherthe first sensed amplitude 164 a satisfies the ascending targetamplitude 168 a for the first signal and the first additional signal.For example, when the amplitude comparator 166 determines that the firstsensed amplitude 164 a is below the ascending target amplitude 168 a,the amplitude comparator 166 can determine that the first sensedamplitude 164 a does not satisfy the ascending target amplitude 168 afor the first signal and the first additional signal. The circuitrycontroller 116 can adjust to increase respective amplitudes of the firstsignal and the first additional signal based on the first sensedamplitude 164 a. For example, the circuitry controller 116 can adjust toincrease amplitude of the first signal and the first additional signalbased on the amplitude comparator 166 determining that the first sensedamplitude 164 a does not satisfy the ascending target amplitude 168 a.The ascending target amplitude 168 a can be based on the respectivepredetermined full amplitude levels of the first signal and the firstadditional signal, so that the circuitry controller 116 can adjust toincrease respective amplitudes of the first signal and the firstadditional signal to the predetermined full amplitude levels.

The circuitry controller 116 can then use the analog differentialamplifier in differentially sensing the voltage across the input 122 aand the additional input 122 b of the ultrasonic transducer, so as todetermine a second sensed amplitude 170 a of the first signal and thefirst additional signal. The amplitude comparator 166 can compare thesecond sensed amplitude 170 a of the first signal and the firstadditional signal to the ascending target amplitude 168 a, for example,to determine whether the second sensed amplitude 170 a of the firstsignal and the first additional signal satisfies the ascending targetamplitude 168 a. For example, when the amplitude comparator 166determines that the second sensed amplitude 170 a of the first signaland the first additional signal meets, or for example exceeds theascending target amplitude 168 a, the amplitude comparator 166 candetermine that the second sensed amplitude 170 a of the first signal andthe first additional signal satisfies the ascending target amplitude 168a. For example, when the amplitude comparator 166 determines that thesecond sensed amplitude 170 a of the first signal and the firstadditional signal satisfies the ascending target amplitude 168 a, thecircuitry controller 116 can determine that increasing the amplitude ofthe first signal and the first additional signal is finished. Forexample, since the ascending target amplitude 168 a can be based on therespective predetermined full amplitude levels of first signal and thefirst additional signal, the circuitry controller 116 can determine thatrespective amplitudes of the first signal and the first additionalsignal have been increased to reach the predetermined full amplitudelevels of first signal and the first additional signal. This comparisoncan determine that ramping up, and increasing the amplitude of the firstsignal and first additional signal, is finished. Similarly, in case ofovershooting the ascending target amplitude 168 a, the circuitrycontroller 116 can then use the analog differential amplifier indifferentially sensing the voltage across the input 122 a and theadditional input 122 b of the ultrasonic transducer, so as to determinedecreasing the amplitude of the first signal and the first additionalsignal to match the ascending target amplitude 168 a.

Ramping up the respective amplitudes of the first signal and the firstadditional signal, as just discussed in various prior examples, canfacilitate activating the ultrasonic transducer 106 at the firstfrequency within the first resonant frequency band of the ultrasonictransducer. For example, by coupling the first signal and the firstadditional signal, the fluid droplet 102 can be reduced by atomizationfrom the first droplet size 102 a to the second droplet size 102 b.Thereafter, the circuitry controller 116 can begin limiting the firstsignal and the first additional signal by ramping down the respectiveamplitudes of the first signal and the first additional signal atultrasonic transducer from the respective predetermined full amplitudelevels of the first signal and the first additional signal to therespective predetermined reduced levels of the first signal and thefirst additional signal.

For example, respective amplitudes of the first signal and the firstadditional signal can be ramped down (e.g., decreased) by the circuitrycontroller 116 from their respective predetermined full amplitude levelsto their respective predetermined reduced amplitude levels at apredetermined ramp down rate. For example, the circuitry controller 116can begin ramping down (e.g., decreasing) respective amplitudes of thefirst signal and the first additional signal at the predetermined rampdown rate. The circuitry controller 116 can continue ramping downrespective amplitudes of the first signal and the first additionalsignal at the predetermined ramp down rate, by decreasing respectiveamplitudes of the first signal and first additional signal, whilerespective predetermined reduced amplitude levels of the first signaland the first additional signal have not yet been reached. Because thecircuitry controller 116 can control and/or decrease and/or set therespective amplitudes of the first signal and first additional signal,the circuitry controller 116 can determine that ramping down of thefirst signal and the first additional is finished. For example, as thecircuitry controller 116 is finishing ramping down, the circuitrycontroller 116 can control and/or decrease and/or set the respectiveamplitudes of the first signal and first additional signal to theirrespective predetermined reduced amplitude levels. For example, afterthe circuitry controller 116 controls and/or decreases and/or sets therespective amplitudes of the first signal and first additional signal totheir respective predetermined reduced amplitude levels, the circuitrycontroller 116 can determine that ramping down (e.g. decreasingamplitude of the first signal and first additional signal) is finished.

In another example of ramping down, the amplitude sensor 162 can includean analog differential amplifier that can differentially sense voltageacross the input 122 a and the additional input 122 b of the ultrasonictransducer 106. The voltage differentially sensed by the analogdifferential amplifier across the input 122 a and the additional input122 b of the ultrasonic transducer 106 is indicative of the respectiveamplitudes of the first signal and the first additional signal inantiphase with one another. The first signal and the first additionalsignal can be ramped down by the circuitry controller 116 from theirrespective predetermined full amplitude levels to their respectivepredetermined reduced amplitude levels at a predetermined ramp downrate. For example, the circuitry controller 116 can begin ramping downthe first signal and the first additional signal at the predeterminedramp down rate. The circuitry controller 116 can continue ramping downthe first signal and the first additional signal at the predeterminedramp down rate, by decreasing respective amplitudes of the first signaland first additional signal, while respective predetermined reducedamplitude levels of the first signal and the first additional signalhave not yet been reached. For example, as the circuitry controller 116is finishing ramping down, the circuitry controller 116 can use theanalog differential amplifier in differentially sensing the voltageacross the input 122 a and the additional input 122 b of the ultrasonictransducer. This measurement can be the first sensed amplitude 164 a andcan be indicative of respective amplitudes of the first signal and thefirst additional signal in antiphase with one another. In this example,the amplitude comparator 166 can compare the first sensed amplitude 164a to the descending target amplitude 168 a, for example, to determinewhether the first sensed amplitude 164 a satisfies the descending targetamplitude 168 a for the first signal and the first additional signal.For example, when the amplitude comparator 166 determines that the firstsensed amplitude 164 a is above the descending target amplitude 168 a,the amplitude comparator 166 can determine that the first sensedamplitude 164 a does not satisfy the descending target amplitude 168 afor the first signal and the first additional signal. The circuitrycontroller 116 can adjust to decrease respective amplitudes of the firstsignal and the first additional signal based on the first sensedamplitude 164 a. For example, the circuitry controller 116 can adjust todecrease amplitude of the first signal and the first additional signalbased on the amplitude comparator 166 determining that the first sensedamplitude 164 a does not satisfy the descending target amplitude 168 a.The descending target amplitude 168 a can be based on the respectivepredetermined reduced amplitude levels of the first signal and the firstadditional signal, so that the circuitry controller 116 can adjust todecrease respective amplitudes of the first signal and the firstadditional signal to the predetermined reduced amplitude levels.

The circuitry controller 116 can then use the analog differentialamplifier in differentially sensing the voltage across the input 122 aand the additional input 122 b of the ultrasonic transducer, so as todetermine a second sensed amplitude 170 a of the first signal and thefirst additional signal. The amplitude comparator 166 can compare thesecond sensed amplitude 170 a of the first signal and the firstadditional signal to the descending target amplitude 168 a, for example,to determine whether the second sensed amplitude 170 a of the firstsignal and the first additional signal satisfies the descending targetamplitude 168 a. For example, when the amplitude comparator 166determines that the second sensed amplitude 170 a of the first signaland the first additional signal meets, or, for example, is below thedescending target amplitude 168 a, the amplitude comparator 166 candetermine that the second sensed amplitude 170 a of the first signal andthe first additional signal satisfies the descending target amplitude168 a. For example, when the amplitude comparator 166 determines thatthe second sensed amplitude 170 a of the first signal and the firstadditional signal satisfies the descending target amplitude 168 a, thecircuitry controller 116 can determine that decreasing the amplitude ofthe first signal and the first additional signal is finished. Forexample, since the descending target amplitude 168 a can be based on therespective predetermined reduced amplitude levels of first signal andthe first additional signal, the circuitry controller 116 can determinethat respective amplitudes of the first signal and the first additionalsignal have been decreased to reach the predetermined reduced amplitudelevels of first signal and the first additional signal. This comparisoncan determine that ramping down, and decreasing the amplitude of thefirst signal and first additional signal, is finished. Similarly, incase of overshooting the descending target amplitude 168 b, thecircuitry controller 116 can then use the analog differential amplifierin differentially sensing the voltage across the input 122 a and theadditional input 122 b of the ultrasonic transducer, so as to determineincreasing the amplitude of the first signal and the first additionalsignal to match the descending target amplitude 168 b.

As just discussed in the various prior examples, the circuitrycontroller 116 can limit the first signal and the first additionalsignal by ramping down the respective amplitudes of the first signal andthe first additional signal at ultrasonic transducer from the respectivepredetermined full amplitude levels of the first signal and the firstadditional signal to the respective predetermined reduced levels of thefirst signal and the first additional signal. Thereafter, the circuitrycontroller 116 can begin determining when to deactivate the first filter112 a (and the first additional filter 112 b) and the ultrasonictransducer 106 based on sensing a first current transient of theultrasonic transducer 106. As shown for example in FIG. 1, an ultrasonictransducer current sensor 172 can be coupled to the ultrasonictransducer 106 to sense current transients, for example, to sense thefirst current transient of the ultrasonic transducer. For example, theultrasonic transducer current sensor 172 can include an AC leveldetector. For example, the AC level detector can include a rectifierfollowed by a low-pass filter. In another example, the AC level detectorcan take a maximum value over a time window which is at least oneelectrical period long.

The ultrasonic transducer current sensor 172 can sense current, forexample, to determine a first current sensing 174 of a first currenttransient of the ultrasonic transducer 106. For example, the circuitrycontroller 116 can include a current transient comparator 176 to comparethe first current sensing 174 of the first current transient of theultrasonic transducer 106 to a current transient threshold 178, forexample, to determine whether the first current sensing 174 of the firstcurrent transient of the ultrasonic transducer 106 satisfies the currenttransient threshold 178. For example, when the current transientcomparator 176 determines that the first current sensing 174 of thefirst current transient of the ultrasonic transducer 106 is above thecurrent transient threshold 178, the current transient comparator 176can determine that the first current sensing 174 of the first currenttransient of the ultrasonic transducer 106 does not satisfy the currenttransient threshold 178. The circuitry controller 116 can delaydeactivating the first filter 112 a (and the first additional filter 112b) and delay deactivating the ultrasonic transducer 106 based on theultrasonic transducer current sensor 172 sensing the first currenttransient of the ultrasonic transducer 106. For example, the circuitrycontroller 116 can delay deactivating the first filter 112 a (and thefirst additional filter 112 b) and delay deactivating the ultrasonictransducer 106 based on the current transient comparator 176 determiningthat the first current sensing 174 of the first current transient of theultrasonic transducer 106 does not satisfy the current transientthreshold 178. The current transient threshold 178 can be based on apredetermined reduced current transient of the ultrasonic transducer106, so that the circuitry controller 116 can delay until the current ofthe ultrasonic transducer 106 reaches the predetermined reduced currenttransient of the ultrasonic transducer 106. The predetermined reducedcurrent transient of the ultrasonic transducer 106 can be a zero currenttransient, or a near zero current transient.

The circuitry controller 116 can also determine whether delaying thedeactivation of the first filter 112 a (and the first additional filter112 b) and delaying the deactivation of the ultrasonic transducer 106 isfinished. The ultrasonic transducer current sensor 172 that can sensecurrent of the ultrasonic transducer 106, for example, can determine asecond current sensing 180 of the first current transient of theultrasonic transducer 106. The current transient comparator 176 cancompare the second current sensing 180 of the first current transient ofthe ultrasonic transducer 106 to the current transient threshold 178,for example, to determine whether the second current sensing 180 of thefirst current transient of the ultrasonic transducer 106 satisfies thecurrent transient threshold 178. For example, when the current transientcomparator 176 determines that the second current sensing 180 of thefirst current transient of the ultrasonic transducer 106 meets, or forexample is lower than the current transient threshold 178, the currenttransient comparator 176 can determine that the second current sensing180 of the first current transient of the ultrasonic transducer 106satisfies the current transient threshold 178. For example, when thecurrent transient comparator 176 determines that second current sensing180 of the first current transient of the ultrasonic transducer 106satisfies the current transient threshold 178, the circuitry controller116 can determine that delaying the deactivation of the first filter 112a (and the first additional filter 112 b) and delaying the deactivationof the ultrasonic transducer 106 is finished. For example, since thecurrent transient threshold 178 can be based on the predeterminedreduced current transient, the circuitry controller 116 can determinethat the first current transient of the ultrasonic transducer 106 hasbeen reduced to reach the predetermined reduced current transient, andso can determine that delaying the deactivation of the first filter 112a (and the first additional filter 112 b) and delaying the deactivationof the ultrasonic transducer 106 is finished.

In the examples just discussed, ultrasonic transducer current sensor 172can be employed in determining whether delaying the deactivation of thefirst filter 112 a (and the first additional filter 112 b) and delayingthe deactivation of the ultrasonic transducer 106 is finished. However,in simpler examples, ultrasonic transducer current sensor 172 may not beneeded. In a simpler example, circuitry controller 116 can determinethat delaying the deactivation of the first filter 112 a (and the firstadditional filter 112 b) and delaying the deactivation of the ultrasonictransducer 106 is finished by using timer 182. For example, timer 182can determine when a predetermined prior time period has elapsed, priorto deactivating the first filter 112 a (and the first additional filter112 b) and deactivating the ultrasonic transducer 106. The predeterminedprior time period can be selected to provide sufficient time for thecurrent transient to die down to a sufficiently reduced currenttransient level.

For example, after finishing ramping down the respective amplitudes ofthe first signal and the first additional signal, the circuitrycontroller 116 can start timer 182 to measure elapsed time. After thetimer 182 determines that the predetermined prior time period haselapsed, the circuitry controller 116 can determine to deactivate thefirst filter 112 a (and the first additional filter 112 b) anddeactivate the ultrasonic transducer 106. After the timer 182 determinesthat the predetermined prior time period has elapsed, the circuitrycontroller 116 can determine that delaying the deactivation of the firstfilter 112 a (and the first additional filter 112 b) and delaying thedeactivation of the ultrasonic transducer 106 is finished.

After the circuitry controller 116 determines that delaying thedeactivation of the first filter 112 a (and the first additional filter112 b) and delaying the deactivation of the ultrasonic transducer 106 isfinished, the circuitry controller 116 can control the filter switchingcircuitry 124 to deactivate the first filter 112 a (and the firstadditional filter 112 b) and deactivate the ultrasonic transducer 106.Further, the circuitry controller 116 can use, for example, timer 182 todelay a predetermined period of time after deactivating the first filter112 a (and the first additional filter 112 b) and deactivating theultrasonic transducer 106. Additionally, after delaying thepredetermined period of time after deactivating the first filter 112 a(and the first additional filter 112 b) and deactivating the ultrasonictransducer 106, the circuitry controller can then activate the secondfilter 114 a (and the second additional filter 114 b) and activate theultrasonic transducer 106.

For example, the filter switching circuitry 124 can be coupled betweenthe circuitry controller 116 and the second filter 114 a (e.g., secondfilter network 114 a) to activate the second filter 114 a (e.g. secondfilter network 114 a) in response to the second control activationsignal received from the circuitry controller 116 at the input 126 ofthe filter switching circuitry 124. Similarly, at the same time, thefilter switching circuitry 124 can be coupled between the circuitrycontroller 116 and the second additional filter 114 b (e.g., secondadditional filter network 114 b) to activate the second additionalfilter 114 b (e.g. second additional filter network 114 b) in responseto the second control activation signal received from the circuitrycontroller 116 at the input 126 of the filter switching circuitry 124.

As shown in the example of FIG. 1, the circuitry controller 116 can becoupled with the input 118 a, 120 a of the first amplifier 108 a togenerate the second signal at the input 122 a of ultrasonic transducer106. Similarly, at the same time, the circuitry controller 116 can becoupled with the additional input 118 b, 120 b of the second amplifier108 b to generate the second additional signal at the additional input122 b of ultrasonic transducer 106. The second signal at the input 122 aof the ultrasonic transducer 106 includes the second frequency withinthe second resonant frequency band of the ultrasonic transducer 106mechanically coupled to the optical surface 104. Similarly, as alreadydiscussed, the second additional signal at the additional input 122 b ofthe ultrasonic transducer 106 likewise can include the second frequencywithin the second resonant frequency band of the ultrasonic transducer106 mechanically coupled to the optical surface 104. The second signaland the second additional signal can be antiphase (e.g.,one-hundred-and-eighty degrees out of phase) with one another.

The circuitry controller 116 can begin ramping up the amplitude of thesecond signal at the ultrasonic transducer 106 from a predeterminedinitial amplitude level of the second signal to a predetermined fullamplitude level of the second signal. At the same time, in a similarlyway, circuitry controller 116 can also begin ramping up the amplitude ofthe second additional signal at the ultrasonic transducer 106 from apredetermined initial amplitude level of the second additional signal toa predetermined full amplitude level of the second additional signal.

While various examples of ramping up the amplitude of the first signaland the first additional signal have already been discussed in detailpreviously herein, amplitude of the second signal and the secondadditional signal can be ramped up by the circuitry controller 116 insimilar ways. Accordingly, application of these previously discussedramping up examples to ramping up the amplitude of the second signal andthe second additional signal is not discussed in detail here. Instead,the reader is directed to the previously discussed ramping up examples,and directed to apply the previously discussed ramping up examples toramping up the amplitude of the second signal and the second additionalsignal.

Ramping up the respective amplitudes of the second signal and the secondadditional signal, as just discussed, can facilitate activating theultrasonic transducer at the second frequency within the second resonantfrequency band of the ultrasonic transducer, for example, by couplingthe second signal and the second additional signal to reduce the fluiddroplet 102 by atomization from the second droplet size 102 b to thethird droplet size 102 c. Thereafter, the circuitry controller 116 canbegin limiting the second signal and the second additional signal byramping down the respective amplitudes of the second signal and thesecond additional signal at ultrasonic transducer from the respectivepredetermined full amplitude levels of the second signal and the secondadditional signal to the respective predetermined reduced levels of thesecond signal and the second additional signal.

While various examples of ramping down amplitude of the first signal andthe first additional signal have already been discussed in detailpreviously herein, amplitude of the second signal and the secondadditional signal can be ramped down by the circuitry controller 116 insimilar ways. Accordingly, application of these previously discussedramping down examples to ramping down amplitude of the second signal andthe second additional signal is not discussed in detail here. Instead,the reader is directed to the previously discussed ramping downexamples, and directed to apply the previously discussed ramping downexamples to ramping down amplitude of the second signal and the secondadditional signal.

As just discussed, the circuitry controller 116 can limit the secondsignal and the second additional signal by ramping down the respectiveamplitudes of the second signal and the second additional signal atultrasonic transducer from the respective predetermined full amplitudelevels of the second signal and the second additional signal to therespective predetermined reduced levels of the second signal and thesecond additional signal. Thereafter, the circuitry controller 116 canbegin determining when to deactivate the second filter 114 a (and thesecond additional filter 114 b) and the ultrasonic transducer 106 basedon sensing a second current transient of the ultrasonic transducer 106.As shown for example in FIG. 1, the ultrasonic transducer current sensor172 can be coupled to the ultrasonic transducer 106 to sense currenttransients, for example, to sense the second current transient of theultrasonic transducer.

The ultrasonic transducer current sensor 172 can sense current, forexample, to determine a first current sensing 174 of the second currenttransient of the ultrasonic transducer 106. For example, the circuitrycontroller 116 can include a current transient comparator 176 to comparethe first current sensing 174 of the second current transient of theultrasonic transducer 106 to the current transient threshold 178, forexample, to determine whether the first current sensing 174 of thesecond current transient of the ultrasonic transducer 106 satisfies thecurrent transient threshold 178. For example, when the current transientcomparator 176 determines that the first current sensing 174 of thesecond current transient of the ultrasonic transducer 106 is above thecurrent transient threshold 178, the current transient comparator 176can determine that the first current sensing 174 of the second currenttransient of the ultrasonic transducer 106 does not satisfy the currenttransient threshold 178. The circuitry controller 116 can delaydeactivating the second filter 114 a (and the second additional filter114 b) and delay deactivating the ultrasonic transducer 106 based on theultrasonic transducer current sensor 172 sensing the second currenttransient of the ultrasonic transducer 106. For example, the circuitrycontroller 116 can delay deactivating the second filter 114 a (and thesecond additional filter 114 b) and delay deactivating the ultrasonictransducer 106 based on the current transient comparator 176 determiningthat the first current sensing 174 of the second current transient ofthe ultrasonic transducer 106 does not satisfy the current transientthreshold 178. The current transient threshold 178 can be based on thepredetermined reduced current transient of the ultrasonic transducer106, so that the circuitry controller 116 can delay until the current ofthe ultrasonic transducer 106 reaches the predetermined reduced currenttransient of the ultrasonic transducer 106. As already mentioned, thepredetermined reduced current transient of the ultrasonic transducer 106can be the zero current transient, or the near zero current transient.

The circuitry controller 116 can also determine whether delaying thedeactivation of the second filter 114 a (and the second additionalfilter 114 b) and delaying the deactivation of the ultrasonic transducer106 is finished. The ultrasonic transducer current sensor 172 that cansense current of the ultrasonic transducer 106, for example, candetermine a second current sensing 180 of the second current transientof the ultrasonic transducer 106. The current transient comparator 176can compare the second current sensing 180 of the second currenttransient of the ultrasonic transducer 106 to the current transientthreshold 178, for example, to determine whether the second currentsensing 180 of the second current transient of the ultrasonic transducer106 satisfies the current transient threshold 178. For example, when thecurrent transient comparator 176 determines that the second currentsensing 180 of the second current transient of the ultrasonic transducer106 meets, or, for example, is lower than the current transientthreshold 178, the current transient comparator 176 can determine thatthe second current sensing 180 of the second current transient of theultrasonic transducer 106 satisfies the current transient threshold 178.For example, when the current transient comparator 176 determines thatthe second current sensing 180 of the second current transient of theultrasonic transducer 106 satisfies the current transient threshold 178,the circuitry controller 116 can determine that delaying thedeactivation of the second filter 114 a (and the second additionalfilter 114 b) and delaying the deactivation of the ultrasonic transducer106 is finished. For example, since the current transient threshold 178can be based on the predetermined reduced current transient, thecircuitry controller 116 can determine that the second current transientof the ultrasonic transducer 106 has been reduced to reach thepredetermined reduced current transient, and so can determine thatdelaying the deactivation of the second filter 114 a (and the secondadditional filter 114 b) and delaying the deactivation of the ultrasonictransducer 106 is finished.

In the examples just discussed, ultrasonic transducer current sensor 172can be employed in determining whether delaying the deactivation of thesecond filter 114 a (and the second additional filter 114 b) anddelaying the deactivation of the ultrasonic transducer 106 is finished.However, in simpler examples, ultrasonic transducer current sensor 172may not be needed. In a simpler example, circuitry controller 116 candetermine that delaying the deactivation of the second filter 114 a (andthe second additional filter 114 b) and delaying the deactivation of theultrasonic transducer 106 is finished by using timer 182. For example,timer 182 can determine when a predetermined prior time period haselapsed, prior to deactivating the second filter 114 a (and the secondadditional filter 114 b) and deactivating the ultrasonic transducer 106.The predetermined prior time period can be selected to providesufficient time for the current transient to die down to a sufficientlyreduced current transient level.

For example, after finishing ramping down the respective amplitudes ofthe second signal and the second additional signal, the circuitrycontroller 116 can start timer 182 to measure elapsed time. After thetimer 182 determines that the predetermined prior time period haselapsed, the circuitry controller 116 can determine to deactivate thesecond filter 114 a (and the second additional filter 114 b) anddeactivate the ultrasonic transducer 106. After the timer 182 determinesthat the predetermined prior time period has elapsed, the circuitrycontroller 116 can determine that delaying the deactivation of thesecond filter 114 a (and the second additional filter 114 b) anddelaying the deactivation of the ultrasonic transducer 106 is finished.

After the circuitry controller 116 determines that delaying thedeactivation of the second filter 114 a (and the second additionalfilter 114 b) and delaying the deactivation of the ultrasonic transducer106 is finished, the circuitry controller 116 can control the filterswitching circuitry to deactivate the second filter 114 a (and thesecond additional filter 114 b) and deactivate the ultrasonic transducer106. Further, the circuitry controller 116 can use, for example, timer182 to delay the predetermined period of time after deactivating thesecond filter 114 a (and the second additional filter 114 b) anddeactivating the ultrasonic transducer 106. Additionally, after delayingthe predetermined period of time after deactivating the second filter114 a (and the second additional filter 114 b) and deactivating theultrasonic transducer 106, a cycle controller 184 of the circuitrycontroller 116 can determine whether to repeat a cycle by once againinitiating activation of first filter 112 a (and first additional filter112 b) and activation of the ultrasonic transducer 106, or instead endthe cycle, based for example on a user control input to the cyclecontroller to end the cycle.

While the foregoing discussions have described ramping up and rampingdown of the first and first additional signals and the second and secondadditional signals, FIG. 1 further shows clamp diodes 186 a, 186 b, 186c, 186 d and transient voltage suppressor (TVS) diodes 188 a, 188 b, 188c, 188 d for protecting circuitry in case current is unexpectedlyinterrupted. As shown in the example of FIG. 1, a first parallelcombination of clamp diode and transient voltage suppressor diode 186 a,188 a can be coupled between the first filter 112 a and a groundreference. Similarly, a second parallel combination of clamp diode andtransient voltage suppressor diode 186 b, 188 b can be coupled betweenthe first additional filter 112 b and the ground reference.Additionally, a third parallel combination of clamp diode and transientvoltage suppressor diode 186 c, 188 c can be coupled between the secondfilter 114 a and the ground reference. A fourth parallel combination ofclamp diode and transient voltage suppressor diode 186 d, 188 d can becoupled between the second additional filter 114 b and the groundreference.

FIG. 2 is a more detailed diagram of the system shown in FIG. 1according to an embodiment. Like example system 100 shown in FIG. 1,example system 200 shown in FIG. 2 can expel fluid from a droplet 102 onan optical surface 104 using an ultrasonic transducer 106 mechanicallycoupled to the optical surface 104. As shown in greater detail in theexample of FIG. 2, first amplifier 108 a can include a first pair ofseries coupled transistors 202 a, 204 a coupled between a DC voltagerail and a ground reference. Respective control gates of the first pairof transistors 202 a, 204 a can be coupled as the input 118 a, 120 a ofthe first amplifier 108 a. The first and second filter networks 112 a,114 a can be coupled to receive an output of the first amplifier 108 aat a series coupling node 206 a between first and second ones of thefirst pair of series coupled transistors 202 a, 204 a.

Similarly, as shown in greater detail in the example of FIG. 2, thesecond amplifier 108 b can include a second pair of series coupledtransistors 202 b, 204 b coupled between the DC voltage rail and theground reference. Respective control gates of the second pair oftransistors 202 b, 204 b can be coupled as the input 118 b, 120 b of thesecond amplifier 108 b. The first and second additional filter networks112 b, 114 b can be coupled to receive an output of the second amplifier108 b at a series coupling node 206 b between first and second ones ofthe second pair of series coupled transistors 202 b, 204 b.

The first filter network 112 a can include a series coupled inductor 208a coupled in series with the output of the first amplifier 108 a at theseries coupling node 206 a between first and second ones of the firstpair of series coupled transistors 202 a, 204 a. The first filternetwork 112 a can also include a capacitor 210 a coupled in series withthe inductor 208 a.

Similarly, second filter network 114 a can include a series coupledinductor 212 a coupled in series with the output of the first amplifier108 a at the series coupling node 206 a between first and second ones ofthe first pair of series coupled transistors 202 a, 204 a. The secondfilter network 114 a can also include a capacitor 214 a coupled inseries with the inductor 212 a.

The first additional filter network 112 b can include a series coupledinductor 208 b coupled in series with the output of the second amplifier108 b at the series coupling node 206 b between first and second ones ofthe second pair of series coupled transistors 202 b, 204 b. The firstadditional filter network 112 b can also include a capacitor 210 bcoupled in series with the inductor 208 b.

Similarly, second additional filter network 114 b can include a seriescoupled inductor 212 b coupled in series with the output of the secondamplifier 108 b at the series coupling node 206 b between first andsecond ones of the second pair of series coupled transistors 202 b, 204b. The second additional filter network 114 b can also include acapacitor 214 b coupled in series with the inductor 212 b.

The first additional filter network 112 b can be tuned (e.g., by itscorresponding filter component values) in a similar way using the sameor similar component values as the first filter network 112 a can betuned (e.g., by its corresponding filter component values). For example,the series coupled inductor 208 a of the first filter network 112 a canhave an inductance L1 that is the same or similar as the inductance L1of the series coupled inductor 208 b of the first additional filternetwork 112 b. Further, the series coupled capacitor 210 a of the firstfilter network 112 a can have a capacitance C1 that is the same orsimilar as the capacitance C1 of the series coupled capacitor 210 b ofthe first additional filter network 112 b.

Similarly, the second additional filter network 114 b can be tuned(e.g., by its corresponding filter component values) in a similar wayusing the same or similar component values as the second filter network114 a can be tuned (e.g., by its corresponding filter component values).For example, the series coupled inductor 212 a of the second filternetwork 114 a can have an inductance L2 that is the same or similar asthe inductance L2 of the series coupled inductor 212 b of the secondadditional filter network 114 b. Further, the series coupled capacitor214 a of the second filter network 114 a can have a capacitance C2 thatis the same or similar as the capacitance C2 of the series coupledcapacitor 214 b of the second additional filter network 114 b.

As shown in the example of FIG. 2, the first filter network 112 a andthe first additional filter network 112 b are tuned by theircorresponding filter component values (e.g., series inductance L1 andseries capacitance C1) within the first resonant frequency band tofacilitate matching the respective first and second output impedance ofthe first and second amplifiers 108 a, 108 b with impedance of theultrasonic transducer 106 mechanically coupled to the optical surface104 and to reduce by atomization the fluid droplet 102 from the firstdroplet size 102 a to the second droplet size 102 b. The second filternetwork 114 a and the second additional filter network 114 b are tunedby their corresponding filter component values (e.g., series inductanceL2 and series capacitance C2) within the second resonant frequency bandto facilitate matching the first and second output impedances of thefirst and second amplifiers 108 a, 108 b with impedance of theultrasonic transducer 106 mechanically coupled to the optical surface104 and to reduce by atomization the fluid droplet 102 from the seconddroplet size 102 b to the third droplet size 102 c.

In the example of FIG. 2, the first filter network 112 a and the firstadditional filter network 112 b can be tuned to the first frequency bytheir corresponding filter component values (e.g., series inductance L1and series capacitance C1) to be higher in frequency than the secondfilter network 114 a and the second additional filter network 114 b astuned to the second frequency by their corresponding filter componentvalues (e.g., series inductance L2 and series capacitance C2).

Although FIG. 2 shows example greater details of the first and secondamplifier 108 a, 108 b than what is shown in FIG. 1, the example of FIG.2 is similar to the example of FIG. 1 as already discussed in detailpreviously herein. Further, although FIG. 2 shows example greaterdetails of the first and first additional filter networks 112 a, 112 band shows example greater details of the second and second additionalfilter networks 114 a, 114 b, the example of FIG. 2 is similar to theexample of FIG. 1 as already discussed in detail previously herein.Accordingly, FIG. 2 is not further discussed here, and the readerdirected instead to the previous discussion of FIG. 1 for discussion ofthose elements that are similar to both the example of FIG. 1 and theexample of FIG. 2.

The examples of FIGS. 1 and 2 show filter switching circuitry to switchthe first and first additional filter networks 112 a, 112 b with thesecond and second additional filter networks 114 a, 114 b. In anotherexample, the forgoing can be extended to include the filter switchingcircuitry to switch a third and third additional filter network (notshown in FIGS. 1 and 2). The filter switching circuitry coupled betweenthe circuitry controller and the third filter network (and between thecircuitry controller and the third additional filter network) toactivate the third filter (and to activate the third additional filter)in response to a third control signal from the circuitry controller. Thethird and third additional filter network can be tuned within a thirdresonant frequency band to facilitate matching the first outputimpedance of the first amplifier with impedance of the ultrasonictransducer mechanically coupled to the surface and to reduce the fluiddroplet by atomization. The circuitry controller can be coupled with theinput of the first amplifier to generate a third signal at the input ofthe ultrasonic transducer, the third signal including a third frequencywithin the third resonant frequency band of the ultrasonic transducermechanically coupled to the surface.

Just discussed was switching circuitry to switch the first and firstadditional filter networks, with the second and second additional filternetworks and with the third and third additional filter networks. In yetanother example, this architecture can be extended even further toinclude the filter switching circuitry to switch a fourth and fourthadditional filter network (not shown in FIGS. 1 and 2). The filterswitching circuitry coupled between the circuitry controller and thefourth filter network (and between the circuitry controller and thefourth additional filter network) to activate the fourth filter (and toactivate the fourth additional filter) in response to a fourth controlsignal from the circuitry controller. The fourth and fourth additionalfilter network can be tuned within a fourth resonant frequency band tofacilitate matching the first output impedance of the first amplifierwith impedance of the ultrasonic transducer mechanically coupled to thesurface and to reduce the fluid droplet by atomization. The circuitrycontroller can be coupled with the input of the first amplifier togenerate a fourth signal at the input of the ultrasonic transducer, thefourth signal including a fourth frequency within the fourth resonantfrequency band of the ultrasonic transducer mechanically coupled to thesurface.

The forgoing examples can be extended even further, to further examplesincluding the switching circuitry to switch activation of fifth, sixth,and so on, filter networks, up to an arbitrary number Nth filternetwork, and up to an arbitrary number Nth resonant frequency band.

The foregoing examples are directed to a plurality of filters tunedwithin respective resonant frequency bands of the ultrasonic transducermechanically coupled to the surface. More broadly, the ultrasonictransducer mechanically coupled to the surface can have a plurality ofresonant frequency bands, and a filter can cover the plurality ofresonant frequency bands. For example, the filter can be the pluralityof filters tuned within respective resonant frequency bands of theultrasonic transducer mechanically coupled to the surface. As anotherexample, the filter can be a single filter covering the plurality ofresonant frequency bands.

In the foregoing examples, a plurality of signals can be generatedhaving respective frequencies within respective resonant frequency bandsof the ultrasonic transducer 106 mechanically coupled to the surface104. The ultrasonic transducer 106 can be activated at the respectivefrequencies within the respective resonant frequency bands using theplurality of signals. Multistage reducing of the fluid droplet 102 byatomization can be carried out in response to activating the ultrasonictransducer 106 using the plurality of signals at the respectivefrequencies within the respective resonant frequency bands. Theplurality of signals can have respective frequency sweeps withinrespective resonant frequency bands of the ultrasonic transducer 106mechanically coupled to the surface 104. Generating the plurality ofsignals can include generating the first signal having the firstfrequency within the first resonant frequency band of the ultrasonictransducer 106 mechanically coupled to the surface 104. Generating theplurality of signals can also include generating the second signalhaving the second frequency within the second resonant frequency band ofthe ultrasonic transducer 106 mechanically coupled to the surface 104.Activating the ultrasonic transducer 106 can include activating theultrasonic transducer at the first frequency within the first resonantfrequency band using the first signal. Activating the ultrasonictransducer 106 can also include activating the ultrasonic transducer atthe second frequency within the second resonant frequency band using thesecond signal. The multistage reducing of the fluid droplet 102 caninclude a first stage, reducing the fluid droplet 102 from the firstdroplet size 102 a to the second droplet size 102 b in response toactivating the ultrasonic sonic transducer 106 using the first signal atthe first frequency within the first resonant frequency band. Themultistage reducing of the fluid droplet 102 can also include a secondstage, reducing the fluid droplet from the second size 102 b to thethird size 102 c in response to activating the ultrasonic transducer 106using the second signal at the second frequency within the secondresonant frequency band.

FIG. 3A is a diagram 300 a of impedance (Ohms in decibels) versusfrequency (logarithmic scale in kilohertz) for an example ultrasonictransducer mechanically coupled to an example optical surface accordingto an embodiment. FIG. 3A shows the example first frequency 302 of anexample three-hundred kilohertz for the example ultrasonic transducermechanically coupled to the example optical surface. The example firstfrequency 302 of the example three-hundred kilohertz can correspond to afirst nominal resonance frequency of a first low impedance resonanceextremity 302 in the diagram of FIG. 3A at the first frequency 302 ofthe example ultrasonic transducer mechanically coupled to the exampleoptical surface. The example first frequency 302 of the examplethree-hundred kilohertz can correspond to the first nominal resonancefrequency of the first low impedance resonance extremity 302 that iscentered within a first resonance band “302band”. More broadly, thefirst frequency 302 is within a first resonance band “302band”. Thefirst resonance band is defined herein as extending in frequency to plusand minus ten percent of the first nominal resonance frequency of thefirst low impedance resonance extremity for the ultrasonic transducermechanically coupled to the optical surface. For example, with theexample first frequency of the example three-hundred kilohertz, thefirst resonance band extends in frequency to plus and minus ten percentof the first nominal resonance frequency of three-hundred kilohertz(e.g. the first resonance band extends in frequency to plus and minusthirty kilohertz from the three-hundred kilohertz, or the firstresonance band extends in frequency from two-hundred-and-seventykilohertz to three-hundred-and-thirty kilohertz).

Further, FIG. 3A shows the example second frequency 304 of an exampletwenty-six kilohertz for the example ultrasonic transducer mechanicallycoupled to the example optical surface. The example second frequency 304of the example twenty-six kilohertz corresponds to a second nominalresonance frequency of a second low impedance resonance extremity 304 inthe diagram of FIG. 3A at the second frequency 304 of the exampleultrasonic transducer mechanically coupled to the example opticalsurface. The example second frequency 304 of the example twenty-sixkilohertz corresponds to the second nominal resonance frequency of thesecond low impedance resonance extremity 304 that is centered within asecond resonance band “304band”. More broadly, the second frequency 302is within a second resonance band “304band”. The second resonance bandis defined herein as extending in frequency to plus and minus tenpercent of the second nominal resonance frequency of the second lowimpedance resonance extremity for the ultrasonic transducer mechanicallycoupled to the optical surface. For example, with the example secondfrequency of the example twenty-six kilohertz, the second resonance bandextends in frequency to plus and minus ten percent of the second nominalresonance frequency of twenty-six kilohertz (e.g. the second resonanceband extends in frequency to plus and minus two and six-tenths kilohertzfrom the twenty-six kilohertz, or the second resonance band extends infrequency from twenty-three-and-four-tenths kilohertz totwenty-eight-and-six-tenths kilohertz).

FIG. 3B is a diagram 300 b of example droplet size reduction versusfrequency according to an embodiment. The example of FIG. 3B shows theexample first frequency 302 of the example three-hundred kilohertz forthe example ultrasonic transducer mechanically coupled to the exampleoptical surface. As shown in the example of FIG. 3B, the example firstfrequency 302 of the example three-hundred kilohertz can reduce thedroplet from the first droplet size 306 (e.g., reduce from tenmillimeters in droplet diameter) to the second droplet size 308 (e.g.,reduce to four millimeters in droplet diameter). This example can be afirst expelling mode.

Further, the example of FIG. 3B shows the example second frequency 304of the example twenty-six kilohertz for the example ultrasonictransducer mechanically coupled to the example optical surface. As shownin the example of FIG. 3B, the example second frequency 304 of theexample twenty-six kilohertz can reduce the droplet from the seconddroplet size 308 (e.g., reduce from four millimeters in dropletdiameter) to the third droplet size 310 (e.g., reduce to eight-tenths ofa millimeter in droplet diameter). This example can be a secondexpelling mode.

While example manners of implementing the example systems 100, 200 thatcan expel fluid from a droplet 102 on an optical surface 104 using anultrasonic transducer 106 mechanically coupled to the optical surface104 of FIGS. 1 and 2, one or more of the elements, processes and/ordevices illustrated in FIGS. 1 and 2 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.

Further, the example systems 100, 200, example ultrasonic transducer106, example first amplifier 108 a, example second amplifier 108 b,example first amplifier impedance 110 a, example second amplifierimpedance 110 b, example first filter network 112 a, example firstadditional filter network 112 b, example second filter network 114 a,example second filter network 114 b, example circuitry controller 116,example first amplifier inputs 118 a, 120 a, example second amplifierinputs 118 b, 120 b, example input of ultrasonic transducer 122 a,example additional input of ultrasonic transducer 122 b, example filterswitching circuitry 124, example input 126 of the filter switchingcircuitry, example first filter switch control 128, example first lowside switch control output 128 a, example first high side switch controloutput 128 b, example first additional low side switch control output128 c, example first additional high side switch control output 128 d,example first low side switch 130 a, example first high side switch 130b, example second filter switch control 138, example second low sideswitch control output 138 a, example second high side switch controloutput 138 b, example second additional low side switch control output138 c, example second additional high side switch control output 138 d,example second low side switch 140 a, example second high side switch140 b, example ultrasonic transducer couplers 142 a, 142 b, examplefirst additional low side switch 150 a, example first additional highside switch 150 b, example second additional low side switch 160 a,example second additional high side switch 160 b, example amplitudesensor 162, example first sensed amplitude 164 a, example firstadditional sensed amplitude 164 b, example amplitude comparator 166,example ascending target amplitude 168 a, example descending targetamplitude 168 b, example second sensed amplitude 170 a, example secondadditional sensed amplitude 170 b, example ultrasonic transducer currentsensor 172, example first current sensing 174, example current transitcomparator 176, example current transient threshold 178, example secondcurrent sensing 180, example timer 182, example cycle controller 184,example clamp diodes 186 a, 186 b, 186 c, 186 d, example transientvoltage suppressor (TVS) diodes 188 a, 188 b, 188 c, 188 d, examplefirst transistor pair 202 a, 204 a, example second transistor pair 202b, 204 b, example outputs of series coupling nodes 206 a, 206 b, exampleseries coupled inductors 208 a, 208 b, 212 a, 212 b, and example seriescoupled capacitors 210 a, 210 b, 214 a, 214 b, as shown in the examplesof FIGS. 1 and 2 may be implemented by hardware, software, firmwareand/or any combination of hardware, software and/or firmware, and may beimplemented by one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)).

Further still, the example systems 100, 200, example fluid droplet 102,example first droplet size 102 a, example second droplet size 102 b,example third droplet size 102 c, example optical surface 104, exampleultrasonic transducer 106, example first amplifier 108 a, example secondamplifier 108 b, example first amplifier impedance 110 a, example secondamplifier impedance 110 b, example first filter network 112 a, examplefirst additional filter network 112 b, example second filter network 114a, example second filter network 114 b, example circuitry controller116, example first amplifier inputs 118 a, 120 a, example secondamplifier inputs 118 b, 120 b, example input of ultrasonic transducer122 a, example additional input of ultrasonic transducer 122 b, examplefilter switching circuitry 124, example input 126 of the filterswitching circuitry, example first filter switch control 128, examplefirst low side switch control output 128 a, example first high sideswitch control output 128 b, example first additional low side switchcontrol output 128 c, example first additional high side switch controloutput 128 d, example first low side switch 130 a, example first highside switch 130 b, example second filter switch control 138, examplesecond low side switch control output 138 a, example second high sideswitch control output 138 b, example second additional low side switchcontrol output 138 c, example second additional high side switch controloutput 138 d, example second low side switch 140 a, example second highside switch 140 b, example ultrasonic transducer couplers 142 a, 142 b,example first additional low side switch 150 a, example first additionalhigh side switch 150 b, example second additional low side switch 160 a,example second additional high side switch 160 b, example amplitudesensor 162, example first sensed amplitude 164 a, example firstadditional sensed amplitude 164 b, example amplitude comparator 166,example ascending target amplitude 168 a, example descending targetamplitude 168 b, example second sensed amplitude 170 a, example secondadditional sensed amplitude 170 b, example ultrasonic transducer currentsensor 172, example first current sensing 174, example current transitcomparator 176, example current transient threshold 178, example secondcurrent sensing 180, example timer 182, example cycle controller 184,example clamp diodes 186 a, 186 b, 186 c, 186 d, example transientvoltage suppressor (TVS) diodes 188 a, 188 b, 188 c, 188 d, examplefirst transistor pair 202 a, 204 a, example second transistor pair 202b, 204 b, example outputs of series coupling nodes 206 a, 206 b, exampleseries coupled inductors 208 a, 208 b, 212 a, 212 b, and example seriescoupled capacitors 210 a, 210 b, 214 a, 214 b, as shown in the examplesof FIGS. 1 and 2, may include one or more elements, processes and/ordevices in addition to, or instead of, those illustrated in FIGS. 1 and2, and/or may include more than one of any or all of the illustratedelements, processes and devices.

When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example systems 100, 200, example ultrasonic transducer 106, examplefirst amplifier 108 a, example second amplifier 108 b, example firstamplifier impedance 110 a, example second amplifier impedance 110 b,example first filter network 112 a, example first additional filternetwork 112 b, example second filter network 114 a, example secondfilter network 114 b, example circuitry controller 116, example firstamplifier input 118 a, 120 a, example second amplifier input 118 b, 120b, example input of ultrasonic transducer 122 a, example additionalinput of ultrasonic transducer 122 b, example filter switching circuitry124, example input 126 of the filter switching circuitry, example firstfilter switch control 128, example first low side switch control output128 a, example first high side switch control output 128 b, examplefirst additional low side switch control output 128 c, example firstadditional high side switch control output 128 d, example first low sideswitch 130 a, example first high side switch 130 b, example secondfilter switch control 138, example second low side switch control output138 a, example second high side switch control output 138 b, examplesecond additional low side switch control output 138 c, example secondadditional high side switch control output 138 d, example second lowside switch 140 a, example second high side switch 140 b, exampleultrasonic transducer couplers 142 a, 142 b, example first additionallow side switch 150 a, example first additional high side switch 150 b,example second additional low side switch 160 a, example secondadditional high side switch 160 b, example amplitude sensor 162, examplefirst sensed amplitude 164 a, example first additional sensed amplitude164 b, example amplitude comparator 166, example ascending targetamplitude 168 a, example descending target amplitude 168 b, examplesecond sensed amplitude 170 a, example second additional sensedamplitude 170 b, example ultrasonic transducer current sensor 172,example first current sensing 174, example current transit comparator176, example current transient threshold 178, example second currentsensing 180, example timer 182, example cycle controller 184, exampleclamp diodes 186 a, 186 b, 186 c, 186 d, example transient voltagesuppressor (TVS) diodes 188 a, 188 b, 188 c, 188 d, example firsttransistor pair 202 a, 204 a, example second transistor pair 202 b, 204b, example outputs of series coupling nodes 206 a, 206 b, example seriescoupled inductors 208 a, 208 b, 212 a, 212 b, and example series coupledcapacitors 210 a, 210 b, 214 a, 214 b, as shown in the examples of FIGS.1 and 2 is/are hereby expressly defined to include a tangible computerreadable storage device or storage disk such as a memory, a digitalversatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storingthe software and/or firmware.

FIGS. 4A-4F show a flowchart representative of example machine readableinstructions that may be executed to implement the example system 100 toexpel fluid of the fluid droplet 102 from the optical surface 104 usingthe ultrasonic transducer 106 mechanically coupled to the opticalsurface 104, according to an embodiment as shown in the example ofFIG. 1. In this example, the machine readable instructions comprise aprogram for execution by a processor such as the processor 512 shown inthe example processor platform 500 discussed below in connection withFIG. 5. The program may be embodied in software stored on a tangiblecomputer readable storage medium such as a CD-ROM, a floppy disk, a harddrive, a digital versatile disk (DVD), a Blu-ray disk, or a memory(e.g., FLASH memory) associated with the processor 512, but the entireprogram and/or parts thereof could alternatively be executed by a deviceother than the processor 512 and/or embodied in firmware or dedicatedhardware. Further, although the example program is described withreference to the flowchart illustrated in FIGS. 4A-4F, many othermethods of implementing the example system 100 to expel fluid of thefluid droplet 102 from the optical surface 104 using the ultrasonictransducer 106 mechanically coupled to the optical surface 104 of thisdisclosure may alternatively be used. For example, the order ofexecution of the blocks may be changed, and/or some of the blocksdescribed may be changed, eliminated, or combined. As used herein, whenthe phrase “at least” is used as the transition term in a preamble of aclaim, it is open-ended in the same manner as the term “comprising” isopen ended. Comprising and all other variants of “comprise” areexpressly defined to be open-ended terms. Including and all othervariants of “include” are also defined to be open-ended terms. Incontrast, the term consisting and/or other forms of consist are definedto be close-ended terms.

As mentioned above, the example processes of FIGS. 4A-4F may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a tangible computer readable storagemedium such as a hard disk drive, a FLASH memory, a read-only memory(ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, arandom-access memory (RAM) and/or any other storage device or storagedisk in which information is stored for any duration (e.g., for extendedtime periods, permanently, for brief instances, for temporarilybuffering, and/or for caching of the information). As used herein, theterm tangible computer readable storage medium is expressly defined toinclude any type of computer readable storage device and/or storage diskand to exclude propagating signals and to exclude transmission media. Asused herein, “tangible computer readable storage medium” and “tangiblemachine readable storage medium” are used interchangeably. Additionallyor alternatively, the example processes of FIGS. 4A-4F may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a FLASH memory, aread-only memory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

A process flow 400 of FIGS. 4A-4F can begin at block 402. At block 402,the optical surface can be oriented within a gravitational field so thata component of the gravitational field that is tangential to the surfaceoperates upon the fluid droplet. For example, as shown in the example ofFIG. 1, the optical surface 104 can be oriented within a gravitationalfield so that a component of the gravitational field that is tangentialto the surface 104 (e.g., as depicted for by downward arrow tangentialto surface 104) operates upon the fluid droplet 102. This orientationcan be achieved, for example, while activating the ultrasonic transducer106 that is mechanically coupled to the optical surface 104 to expelfluid of the fluid droplet 102 from the optical surface. For example,the foregoing orienting of the optical surface 104 can be orienting theoptical surface 104 within the gravitational field so that the componentof the gravitational field that is tangential to the optical surface 104is greater than a component of the gravitation field that is normal intothe optical surface 104.

Next, as shown in example of FIG. 4A, at block 404 the first filter (andthe first additional filter) tuned within the first resonant frequencyband can be activated to facilitate impedance matching of the firstamplifier (and the second amplifier) with impedance of the ultrasonictransducer. As shown for example in FIG. 1, the first filter 112 a(e.g., first filter network 112 a) is tuned (e.g., by its correspondingfilter component values) within the first resonant frequency band tofacilitate matching the first output impedance 110 a of the firstamplifier 108 a with impedance of the ultrasonic transducer 106mechanically coupled to the optical surface 104. Similarly, as shown forexample in FIG. 1, the first additional filter 112 b (e.g., firstadditional filter network 112 b) is tuned (e.g., by its correspondingfilter component values) within the first resonant frequency band tofacilitate matching the second output impedance 110 b of the secondamplifier 108 b with impedance of the ultrasonic transducer 106mechanically coupled to the optical surface 104. In the example of FIG.1, filter activation (and deactivation), as well as activation (anddeactivation) of the ultrasonic transducer 106, can be carried out byfilter switching circuitry 124, which is depicted in the drawings usingstippled lines. For example, the filter switching circuitry 124 can becoupled between the circuitry controller 116 and the first filter 112 a(e.g., first filter network 112 a) to activate the first filter 112 a(e.g. first filter network 112 a) in response to a first controlactivation signal received from the circuitry controller 116 at an input126 of the filter switching circuitry 124. Similarly, at the same time,the filter switching circuitry 124 can be coupled between the circuitrycontroller 116 and the first additional filter 112 b (e.g., firstadditional filter network 112 b) to activate the first additional filter112 b (e.g. first additional filter network 112 b) in response to thefirst control activation signal received from the circuitry controller116 at the input 126 of the filter switching circuitry 124.

Next, as shown in example of FIG. 4A, at block 406 the first signal (andthe first additional signal) including the first frequency within thefirst resonant frequency band of the ultrasonic transducer can begenerated. For example, as shown in the example of FIG. 1, the circuitrycontroller 116 can be coupled with the input 118 a, 120 a of the firstamplifier 108 a to generate the first signal at the input 122 a ofultrasonic transducer 106. Similarly, at the same time, the circuitrycontroller 116 can be coupled with the additional input 118 b, 120 b ofthe second amplifier 108 b to generate the first additional signal atthe additional input 122 b of ultrasonic transducer 106. The firstsignal at the input 122 a of the ultrasonic transducer 106 includes thefirst frequency within the first resonant frequency band of theultrasonic transducer 106 mechanically coupled to the optical surface104. Similarly, the first additional signal at the additional input 122b of the ultrasonic transducer 106 likewise can include the firstfrequency within the first resonant frequency band of the ultrasonictransducer 106 mechanically coupled to the optical surface 104.

Next, as shown in the example of FIG. 4A, at block 408 a ramping up ofthe amplitude of the first signal (and of the first additional signal)at ultrasonic transducer can begin from the predetermined initialamplitude level of first signal (and of the first additional signal) tothe predetermined full amplitude level of first signal (and of the firstadditional signal). For example, as shown in the example of FIG. 1, thecircuitry controller 116 can begin ramping up the amplitude of the firstsignal at the ultrasonic transducer 106 from a predetermined initialamplitude level of the first signal to a predetermined full amplitudelevel of the first signal. At the same time, in a similarly way,circuitry controller 116 can also begin ramping up the amplitude of thefirst additional signal at the ultrasonic transducer 106 from apredetermined initial amplitude level of the first additional signal toa predetermined full amplitude level of the first additional signal. Forexample, respective amplitudes of the first signal and the firstadditional signal can be ramped up (e.g., increased) by the circuitrycontroller 116 from their respective predetermined initial amplitudelevels to their respective predetermined full amplitude levels at apredetermined ramp up rate.

Next, as shown in the example of FIG. 4A, at block 410 an amplitude ofthe first signal can be sensed (and an amplitude of the first additionalsignal can be sensed). For example, as shown in the example of FIG. 1,the circuitry controller 116 can include an amplitude sensor 162 thatcan sense amplitude of the first signal, for example, to determine afirst sensed amplitude 164 a of the first signal and the firstadditional signal.

Next, as shown in the example of FIG. 4A, at block 412 an amplitude ofthe first signal and the first additional signal can be adjusted (e.g.,increased) based on the sensed amplitude of the first signal and thefirst additional signal. Next, as shown in the example of FIG. 4A, atdecision block 414 it is determined whether adjusting the amplitude ofthe first signal is finished (and whether adjusting the amplitude of thefirst additional signal is finished). For example, at decision block 414it is determined whether the ramping up adjustment to increase amplitudeof the first signal is finished (and whether the ramping up adjustmentto increase amplitude of the first additional signal is finished). If itis determined by the circuitry controller that adjusting the amplitudeof the first signal is not finished, for example ramping up adjustmentis not finished (and, for example, that adjusting the amplitude of thefirst additional signal is not finished, for example, ramping up is notfinished), then flow of execution can be redirected to block 410 tosense amplitude of the first signal (and, for example, to senseamplitude of the first additional signal and the first additionalsignal). However, if it is determined by the circuitry controller thatthe adjusting the amplitude of the first signal is finished for example,ramping up is finished (and, for example, that the adjusting theamplitude of the first additional signal is finished, for example,ramping up is finished), then flow of execution can be directed to block416 of FIG. 4B.

Next, as shown in the example of FIG. 4B, at block 416 the ultrasonictransducer is activated at the first frequency within the first resonantfrequency band of the ultrasonic transducer by coupling the first signal(and the first additional signal) with the ultrasonic transducer. Atblock 418, the activated ultrasonic transducer can expel fluid from thefluid droplet to reduce the fluid droplet by atomization from the firstdroplet size to the second droplet size. For example, as shown in theexample of FIG. 1, the ultrasonic transducer 106 can be activated at thefirst frequency within the first resonant frequency band of theultrasonic transducer 106, for example, by coupling the first signal andthe first additional signal to reduce the fluid droplet 102 byatomization from the first droplet size 102 a to the second droplet size102 b.

Next, as shown in the example of FIG. 4B, at block 420 the limiting ofthe first signal (and limiting of the first additional signal) byramping down the amplitude of first signal (and by ramping down thefirst additional signal) at the ultrasonic transducer can begin. Forexample, respective amplitudes of the first signal and the firstadditional signal can be ramped down (e.g., decreased) by the circuitrycontroller from their respective predetermined full amplitude levels totheir respective predetermined reduced amplitude levels at apredetermined ramp down rate. For example, such limiting can includeramping down from the predetermined full amplitude level of the firstsignal to the predetermined reduced level of the first signal, and caninclude ramping down from the predetermined full amplitude level of thefirst additional signal to the predetermined reduced level of the firstadditional signal. At block 422 the amplitude of first signal can besensed (and the amplitude of the first additional signal can be sensed).For example, as shown in the example of FIG. 1, the amplitude sensor 162can sense amplitude of the first signal and the first additional signal,for example, to determine the first sensed amplitude 164 a of the firstsignal and the first additional signal when the first signal and thefirst additional signal are being limited and/or reduced.

As shown in the example of FIG. 4B, at block 424 amplitude of the firstsignal can be adjusted (e.g., decreased) based on sensed amplitude offirst signal and the first additional signal. At decision block 426 itis determined by the circuitry controller whether adjusting theamplitude of the first signal is finished (and whether adjusting theamplitude of the first additional signal is finished). For example, atdecision block 426 it is determined whether the ramping down adjustmentto decrease amplitude of the first signal is finished (and whether theramping down adjustment to decrease amplitude of the first additionalsignal is finished). If it is determined that adjusting the amplitude ofthe first signal is not finished, for example ramping down adjustment isnot finished (and, for example, that adjusting the amplitude of thefirst additional signal is not finished, for example, ramping down isnot finished), then flow of execution can be redirected to block 422 tosense amplitude of the first signal (and, for example, to senseamplitude of the first additional signal). However, if it is determinedby the circuitry controller that adjusting the amplitude of the firstsignal is finished for example, ramping down is finished (and, forexample, that adjusting the amplitude of the first additional signal isfinished, for example, ramping down is finished), then flow of executioncan be directed to block 428 of FIG. 4C.

As shown in the example of FIG. 4C, at block 428 determining when todeactivate first filter (and deactivate the first additional filter) anddeactivate the ultrasonic transducer based on sensing the first currenttransient of ultrasonic transducer can begin. At block 430 the firstcurrent transient of ultrasonic transducer can be sensed. At block 432,delay the deactivation of the first filter (and deactivation of thefirst additional filter) and deactivation of the ultrasonic transducercan be based on the sensed first current transient of ultrasonictransducer. For example, as shown in the example of FIG. 1, thecircuitry controller 116 can begin determining when to deactivate thefirst filter 112 a (and the first additional filter 112 b) and theultrasonic transducer 106 based on sensing the first current transientof the ultrasonic transducer 106. As shown for example in FIG. 1, theultrasonic transducer current sensor 172 can be coupled to theultrasonic transducer 106 to sense current transients, for example, tosense the first current transient of the ultrasonic transducer.

As shown in FIG. 4C, at decision block 434 it can be determined by thecircuitry controller whether delaying deactivation of the first filter(and deactivation of the first additional filter) and deactivation ofthe ultrasonic transducer based on the sensed first current transient ofthe ultrasonic transducer is finished. If it is determined that delayingsuch deactivation is not finished, then flow of execution can beredirected to block 430 to sense amplitude of the first currenttransient of the ultrasonic transducer. However, if it is determined bythe circuitry controller that delaying such deactivation is finished,then flow of execution can be directed to block 436 of FIG. 4C. At block436 of FIG. 4C, the first filter and the first additional filter and theultrasonic transducer are deactivated, when delaying such deactivationis finished.

Next, after deactivating the first filter (and the first additionalfilter) and the ultrasonic transducer, as shown in the example of FIG.4C, at block 438 there can be a delay of a predetermined period of time.For example, as shown in the example of FIG. 1, the circuitry controller116 can use, for example, timer 182 to delay the predetermined period oftime after deactivating the first filter 112 a (and the first additionalfilter 112 b) and deactivating the ultrasonic transducer 106.

Next, as shown in the example of FIG. 4D, at block 440 the second filter(and the second additional filter) tuned within the second resonantfrequency band can be activated to facilitate impedance matching of thefirst amplifier (and the second amplifier) with impedance of theultrasonic transducer. As shown for example in FIG. 1, the second filter114 a (e.g., second filter network 114 a) is tuned (e.g., by itscorresponding filter component values) within the second resonantfrequency band to facilitate matching the first output impedance 110 aof the first amplifier 108 a with impedance of the ultrasonic transducer106 mechanically coupled to the optical surface 104. Similarly, as shownfor example in FIG. 1, the second additional filter 114 b (e.g., secondadditional filter network 114 b) is tuned (e.g., by its correspondingfilter component values) within the second resonant frequency band tofacilitate matching the second output impedance 110 b of the secondamplifier 108 b with impedance of the ultrasonic transducer 106mechanically coupled to the optical surface 104.

Next, as shown in example of FIG. 4D, at block 442 the second signal(and the second additional signal) including the second frequency withinthe second resonant frequency band of the ultrasonic transducer can begenerated. For example, as shown in the example of FIG. 1, the circuitrycontroller 116 can be coupled with the input 118 a, 120 a of the firstamplifier 108 a to generate the second signal at the input 122 a ofultrasonic transducer 106. Similarly, at the same time, the circuitrycontroller 116 can be coupled with the additional input 118 b, 120 b ofthe second amplifier 108 b to generate the second additional signal atthe additional input 122 b of ultrasonic transducer 106. The secondsignal at the input 122 a of the ultrasonic transducer 106 includes thesecond frequency within the second resonant frequency band of theultrasonic transducer 106 mechanically coupled to the optical surface104. Similarly, the second additional signal at the additional input 122b of the ultrasonic transducer 106 likewise can include the secondfrequency within the second resonant frequency band of the ultrasonictransducer 106 mechanically coupled to the optical surface 104.

Next, as shown in the example of FIG. 4D, at block 444 a ramping up ofthe amplitude of the second signal (and of the second additional signal)at ultrasonic transducer can begin from the predetermined initialamplitude level of second signal (and of the second additional signal)to the predetermined full amplitude level of second signal (and of thesecond additional signal). For example, respective amplitudes of thesecond signal and the second additional signal can be ramped up (e.g.,increased) by the circuitry controller from their respectivepredetermined initial amplitude levels to their respective predeterminedfull amplitude levels at a predetermined ramp up rate. For example, asshown in the example of FIG. 1, the circuitry controller 116 can beginramping up the amplitude of the second signal at the ultrasonictransducer 106 from a predetermined initial amplitude level of thesecond signal to a predetermined full amplitude level of the secondsignal. At the same time, in a similarly way, circuitry controller 116can also begin ramping up the amplitude of the second additional signalat the ultrasonic transducer 106 from a predetermined initial amplitudelevel of the second additional signal to a predetermined full amplitudelevel of the second additional signal.

Next, as shown in the example of FIG. 4D, at block 446 an amplitude ofthe second signal can be sensed (and an amplitude of the secondadditional signal can be sensed). For example, as shown in the exampleof FIG. 1, the circuitry controller 116 can include an amplitude sensor162 that can sense amplitude of the second signal and the secondadditional signal.

Next, as shown in the example of FIG. 4D, at block 448 the amplitude ofthe second signal and the second additional signal can be adjusted(e.g., increased) based on the sensed amplitude of the second signal andthe second additional signal. Next, as shown in the example of FIG. 4D,at decision block 450 it is determined by the circuitry controllerwhether the adjusting the amplitude of the second signal is finished(and whether the adjusting the amplitude of the second additional signalis finished). For example, at decision block 450 it is determinedwhether the ramping up adjustment to increase amplitude of the secondsignal is finished (and whether the ramping up adjustment to increaseamplitude of the second additional signal is finished). If it isdetermined that the adjusting the amplitude of the second signal and thesecond additional signal is not finished, for example ramping upadjustment is not finished, then flow of execution can be redirected toblock 446 to sense amplitude of the second signal (and, for example, tosense amplitude of the second additional signal). However, if it isdetermined by the circuitry controller that the adjusting the amplitudeof the second signal is finished for example, ramping up is finished(and, for example, that the adjusting amplitude of the second additionalsignal is finished, for example, ramping up is finished), then flow ofexecution can be directed to block 452 of FIG. 4E.

Next, as shown in the example of FIG. 4E, at block 452 the ultrasonictransducer is activated at the second frequency within the secondresonant frequency band of the ultrasonic transducer by coupling thesecond signal (and the second additional signal) with the ultrasonictransducer. At block 454, the activated ultrasonic transducer can expelfluid from the droplet to reduce the droplet by atomization from thesecond droplet size to the third droplet size. For example, as shown inthe example of FIG. 1, the ultrasonic transducer 106 can be activated atthe second frequency within the second resonant frequency band of theultrasonic transducer 106, for example, by coupling the second signaland the second additional signal to reduce the fluid droplet 102 byatomization from the second droplet size 102 b to the third droplet size102 c.

Next, as shown in the example of FIG. 4E, at block 456 the limiting ofthe second signal (and limiting of the second additional signal) byramping down the amplitude of second signal (and by ramping down thesecond additional signal) at the ultrasonic transducer can begin. Forexample, respective amplitudes of the second signal and the secondadditional signal can be ramped down (e.g., decreased) by the circuitrycontroller from their respective predetermined full amplitude levels totheir respective predetermined reduced amplitude levels at apredetermined ramp down rate. For example, such limiting can includeramping down from the predetermined full amplitude level of the secondsignal to the predetermined reduced level of the second signal, and caninclude ramping down from the predetermined full amplitude level of thesecond additional signal to the predetermined reduced level of thesecond additional signal. At block 458 the amplitude of second signalcan be sensed (and the amplitude of the second additional signal can besensed). As shown in the example of FIG. 4E, at block 460 amplitude ofthe second signal can be adjusted based on sensed amplitude of secondsignal, and similarly, amplitude of the second additional signal can beadjusted based on sensed amplitude of second additional signal.

As shown in the example of FIG. 4E, at decision block 462 it isdetermined by the circuitry controller whether the adjusting theamplitude of the second signal is finished (and whether the adjustingamplitude of the second additional signal is finished). For example, atdecision block 462 it is determined by the circuitry controller whetherthe ramping down adjustment to decrease amplitude of the second signalis finished (and whether the ramping down adjustment to decreaseamplitude of the second additional signal is finished). If it isdetermined by the circuitry controller that the adjusting amplitude ofthe second signal is not finished, for example ramping down adjustmentis not finished (and, for example, that the adjusting amplitude of thesecond additional signal is not finished, for example, ramping down isnot finished), then flow of execution can be redirected to block 458 tosense amplitude of the second signal (and, for example, to senseamplitude of the second additional signal). However, if it is determinedby the circuitry controller that the adjusting amplitude of the secondsignal is finished for example, ramping down is finished (and, forexample, that the adjusting amplitude of the second additional signal isfinished, for example, ramping down is finished), then flow of executioncan be directed to block 464 of FIG. 4F.

As shown in the example of FIG. 4F, at block 464 determining when todeactivate second filter (and deactivate the second additional filter)and deactivate the ultrasonic transducer based on sensing the secondcurrent transient of ultrasonic transducer can begin. At block 466 thesecond current transient of ultrasonic transducer can be sensed. Atblock 468, delay in deactivating the second filter (and deactivating thesecond additional filter) and deactivating the ultrasonic transducer canbe based on the sensed second current transient of ultrasonictransducer. For example, as shown in the example of FIG. 1, thecircuitry controller 116 can begin determining when to deactivate thesecond filter 114 a (and the second additional filter 114 b) and theultrasonic transducer 106 based on sensing the second current transientof the ultrasonic transducer 106. As shown for example in FIG. 1, theultrasonic transducer current sensor 172 can be coupled to theultrasonic transducer 106 to sense current transients, for example, tosense the second current transient of the ultrasonic transducer.

As shown in FIG. 4F, at decision block 470 it can be determined by thecircuitry controller whether delaying deactivation of the second filter(and deactivation of the second additional filter) and deactivation ofthe ultrasonic transducer based on the sensed second current transientof the ultrasonic transducer is finished. If it is determined by thecircuitry controller that delaying such deactivation is not finished,then flow of execution can be redirected to block 466 to sense amplitudeof the second current transient of the ultrasonic transducer. However,if it is determined by the circuitry controller that delaying suchdeactivation is finished, then flow of execution can be directed toblock 472 of FIG. 4F. At block 472 of FIG. 4F, the second filter and thesecond additional filter and the ultrasonic transducer are deactivated,when delaying such deactivation is finished.

Next, after deactivating the second filter (and the second additionalfilter) and the ultrasonic transducer, as shown in the example of FIG.4F, at block 474 there can be a delay of a predetermined period of time.For example, as shown in the example of FIG. 1, the circuitry controller116 can use, for example, timer 182 to delay the predetermined period oftime after deactivating the second filter 114 a (and the secondadditional filter 114 b) and deactivating the ultrasonic transducer 106.

Next, as shown in the example of FIG. 4F, at decision block 476 it isdetermined whether to end the cycle of expelling fluid from the opticalsurface. For example, if a control input registered at a time determinesthat the cycle is not to end at that time, then flow execution transfersto block 404 shown in FIG. 4A. However, if a control input registered atthat time determines that the cycle is to end at that time, then afterblock 476, the example method 400 can end.

FIG. 5 is a block diagram of an example processing platform capable ofexecuting the machine readable instructions of FIGS. 4A-4F to implementthe example system to expel fluid from the droplet on the opticalsurface using the ultrasonic transducer mechanically coupled to theoptical surface, according to an embodiment as shown in the example ofFIG. 1.

The processor platform 500 can be, for example, a server, a personalcomputer, a mobile device (e.g., a cell phone, a smart phone, a tabletsuch as an iPad™), a personal digital assistant (PDA), an Internetappliance, a DVD player, a CD player, a digital video recorder, aBlu-ray player, a gaming console, a personal video recorder, a set topbox, or any other type of computing device.

The processor platform 500 of the illustrated example includes aprocessor 512. The processor 512 of the illustrated example is hardware.For example, the processor 512 can be implemented by one or moreintegrated circuits, logic circuits, microprocessors or controllers fromany desired family or manufacturer. The hardware of processor 512 can bevirtualized using virtualization such as Virtual Machines and/orcontainers. The processor 512 can implement example circuitry controller116, including example amplitude sensor 162, example first sensedamplitude 164 a, example first additional sensed amplitude 164 b,example amplitude comparator 166, example ascending target amplitude 168a, example descending target amplitude 168 b, example second sensedamplitude 170 a, example second additional sensed amplitude 170 b,example ultrasonic transducer current sensor 172, example first currentsensing 174, example current transient comparator 176, example currenttransient threshold 178, example second current sensing 180, exampletimer 182 and example cycle controller 184. The processor 512 can alsoimplement example filter switching circuitry 124 including example firstfilter switch controller 128 and second filter switch controller 138.The processor 512, in implementing circuitry controller 116, cangenerate the first signal (and first additional signal) having the firstfrequency and can generate the second signal (and second additionalsignal) having the second frequency using methods such as pulse-widthmodulation (PWM) or direct digital synthesis (DDS).

The processor 512 of the illustrated example includes a local memory 513(e.g., a cache). The processor 512 of the illustrated example is incommunication with a main memory including a volatile memory 514 and anon-volatile memory 516 via a bus 518. The volatile memory 514 may beimplemented by Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM)and/or any other type of random access memory device. The non-volatilememory 516 may be implemented by FLASH memory and/or any other desiredtype of memory device. Access to the main memory 514, 516 is controlledby a memory controller.

The processor platform 500 of the illustrated example also includes aninterface circuit 520. The interface circuit 520 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 522 are connectedto the interface circuit 520. The input device(s) 522 permit(s) a userto enter data and commands into the processor 512. The input device(s)can be implemented by, for example, an audio sensor, a microphone, acamera (still or video), a keyboard, a button, a mouse, a touchscreen, atrack-pad, a trackball, isopoint and/or a voice recognition system.

One or more output devices 524 are also connected to the interfacecircuit 520 of the illustrated example. The output devices 524 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube display (CRT), a touchscreen, atactile output device, a printer and/or speakers). The interface circuit520 of the illustrated example, thus, typically includes a graphicsdriver card, a graphics driver chip or a graphics driver processor.

The interface circuit 520 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network526 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 500 of the illustrated example also includes oneor more mass storage devices 528 for storing software and/or data.Examples of such mass storage devices 528 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, RAIDsystems, and digital versatile disk (DVD) drives.

The coded instructions 532 of FIG. 5 may be stored in the mass storagedevice 528, in the volatile memory 514, in the non-volatile memory 516,and/or on a removable tangible computer readable storage medium such asa CD or DVD.

Modifications are possible in the described embodiments, and otherembodiments are possible, within the scope of the claims.

What is claimed is:
 1. Apparatus comprising: a signal generator having agenerator output, the signal generator configured to generate first andsecond signals at the generator output, the first signal having a firstfrequency, and the second signal having a second frequency; andswitching circuitry having a circuitry input and a circuitry output, thecircuitry input coupled to the generator output, the circuitry outputadapted to be coupled to an ultrasonic transducer mechanically coupledwith a surface, and the switching circuitry configured to: provide thefirst signal to the ultrasonic transducer at the first frequency toreduce a fluid droplet on the surface from a first size to a secondsize; and provide the second signal to the ultrasonic transducer at thesecond frequency to reduce the fluid droplet from the second size to athird size.
 2. The apparatus of claim 1, wherein the first frequency ishigher than the second frequency.
 3. The apparatus of claim 1, whereinthe first frequency is within a first resonant frequency band of theultrasonic transducer, and the second frequency is within a secondresonant frequency band of the ultrasonic transducer.
 4. The apparatusof claim 1, wherein the surface is an optical surface.